US20130071716A1 - Thermal management device - Google Patents
Thermal management device Download PDFInfo
- Publication number
- US20130071716A1 US20130071716A1 US13/235,009 US201113235009A US2013071716A1 US 20130071716 A1 US20130071716 A1 US 20130071716A1 US 201113235009 A US201113235009 A US 201113235009A US 2013071716 A1 US2013071716 A1 US 2013071716A1
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- United States
- Prior art keywords
- thermal management
- management device
- insulator
- energy storage
- heater
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
- H01M10/00—Secondary cells; Manufacture thereof
- H01M10/36—Accumulators not provided for in groups H01M10/05-H01M10/34
- H01M10/39—Accumulators not provided for in groups H01M10/05-H01M10/34 working at high temperature
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
- H01M10/00—Secondary cells; Manufacture thereof
- H01M10/60—Heating or cooling; Temperature control
- H01M10/61—Types of temperature control
- H01M10/615—Heating or keeping warm
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
- H01M10/00—Secondary cells; Manufacture thereof
- H01M10/60—Heating or cooling; Temperature control
- H01M10/65—Means for temperature control structurally associated with the cells
- H01M10/657—Means for temperature control structurally associated with the cells by electric or electromagnetic means
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- H—ELECTRICITY
- H05—ELECTRIC TECHNIQUES NOT OTHERWISE PROVIDED FOR
- H05B—ELECTRIC HEATING; ELECTRIC LIGHT SOURCES NOT OTHERWISE PROVIDED FOR; CIRCUIT ARRANGEMENTS FOR ELECTRIC LIGHT SOURCES, IN GENERAL
- H05B1/00—Details of electric heating devices
- H05B1/02—Automatic switching arrangements specially adapted to apparatus ; Control of heating devices
- H05B1/0227—Applications
- H05B1/0252—Domestic applications
- H05B1/0275—Heating of spaces, e.g. rooms, wardrobes
- H05B1/0286—Heat storages
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- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
- Y02E60/00—Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
- Y02E60/10—Energy storage using batteries
Definitions
- the subject matter disclosed herein relates to thermal management devices, and more particularly, to thermal management devices for use with rechargeable batteries.
- Rechargeable batteries may have challenges in thermal management and thermal regulation, particularly as the life span of the rechargeable energy storage cells increases. Premature failure of a thermal management device renders a rechargeable battery inoperative, increasing maintenance and repair costs and reducing the effectiveness of the battery system. These challenges with existing thermal management devices affect the efficiency of the battery operations and also the efficiency and operating costs of the system or systems supported by the battery.
- thermal management device may be desirable to have a thermal management device that differs from those that are currently available.
- the thermal management device has an insulator with a maximum use temperature greater than about 200 degrees Celsius, and a heating element with at least one heater leg.
- the heater leg contacts the insulator and is configured to supply thermal energy, such as to a rechargeable energy storage cell.
- the heating element has lead wires configured to provide a parallel electrical connection between the at least one heater leg and a current source for the thermal management device.
- a thermal management device in another embodiment, includes a plurality of insulator panels with a maximum use temperature of at least 500 degrees Celsius, and a heating element comprising at least two heater legs electrically connected in parallel, where each heater leg contacts at least one of the insulator panels and is configured to supply thermal energy, such as to a rechargeable energy storage cell.
- the heating element has lead wires configured to provide a parallel electrical connection between the heater legs and a current source.
- a thermal management device in another embodiment, includes an insulator with a maximum use temperature greater than about 500 degrees Celsius, and a heating element with at least two heater legs electrically connected in parallel.
- the heater legs contact the insulator and are configured to supply thermal energy to a plurality of energy storage cells.
- each of the parallel heater legs is configured to provide substantially uniform heat flux over at least one surface of the device.
- the energy storage device includes a plurality of energy storage cells having an operating temperature of at least 250 degrees Celsius, and a thermal management device.
- the thermal management device has an insulator with a maximum use temperature of at least 500 degrees Celsius, and a heating element contacting the insulator and having a plurality of heater legs electrically connected in parallel.
- the heating element is configured to supply thermal energy to the plurality of energy storage cells.
- the heating element includes lead wires configured to provide a parallel electrical connection between the heater legs and a current source.
- FIG. 1 is a schematic view of a thermal management device:
- FIG. 2 is a schematic view of a thermal management device in a battery enclosure:
- FIG. 3 is a cross-section view of a thermal management device having a housing
- FIG. 4 is a perspective view of a first heating element
- FIG. 5 is a top view of a second heating element
- FIG. 6 is a top view of third heating element
- FIG. 7 is a top view of fourth heating element
- FIG. 8 is a top view of fifth heating element
- FIG. 9 is a top view of sixth heating element
- FIG. 10 is a perspective view of a portion of a thermal management device
- FIG. 11 is a side view of a second thermal management device
- FIG. 12 is a side view of a third thermal management device
- FIG. 13 is a side view of a fourth thermal management device
- FIG. 14 is a top view of a strain relief
- FIG. 15 is a cross-section view of a strain relief
- FIG. 16 is a cross-section view of another strain relief
- FIG. 17 is a top view of a thermal management device with a strain relief
- FIG. 18 is a view of a thermal management device with a strain relief with the bottom insulator removed;
- FIG. 19 is a bottom view of the thermal management device of FIG. 18 with the bottom insulator installed;
- FIG. 20 is a top view of another thermal management device
- FIG. 21 is a top view of another thermal management device
- FIG. 22 is a thermal profile of an energy storage device
- FIG. 23 is a heat flux profile of a thermal management device
- FIG. 24 is a thermal profile of an energy storage device with substantially uniform cell temperature
- FIG. 25 is a cross-section of an energy storage device having a thermal management device
- FIG. 26 is a perspective view of an energy storage device with the top cover removed;
- FIG. 27 is a simulated thermal profile of a battery having a thermal management device.
- FIG. 28 is a schematic view of another thermal management device in a battery enclosure.
- the subject matter disclosed herein relates to a thermal management device, and an energy storage device, such as a rechargeable battery system that includes a thermal management device.
- a thermal management device and an energy storage device, such as a rechargeable battery system that includes a thermal management device.
- FIGS. 1 through 28 embodiments of a thermal management device and an energy storage device having a thermal management device are disclosed.
- a thermal management device includes an insulator, a heating element, and lead wires configured to provide a parallel electrical connection between the heating element and a current source.
- the heating element may have one or more heater legs electrically connected in parallel, where the heater legs contact the insulator and are configured to supply thermal energy to a structure to be heated by the thermal management device, such as an energy storage cell (electrochemical cell) of a rechargeable battery.
- the insulator may be a sheet silicate or other insulating material capable of supporting the heating element at the operating temperature of the thermal management device.
- the lead wires are configured to provide a parallel electrical connection between the heating element and a current source.
- the current source may be the same current source used to charge the rechargeable battery, or it may be a separate current source.
- the thermal management device 10 has a heating element with four heater legs 12 electrically connected in parallel.
- the heater legs 12 are connected to bus bars 14 , but in other embodiments, the heater legs 12 may be connected directly to each other to form the electrically parallel connection.
- the plurality of heater legs improves the fault tolerance of the thermal management device, which may continue to operate even if one or more of the heater legs becomes inoperative.
- the thermal management device 10 also includes a pair of positive lead wires 16 providing an electrical connection to the heating element. The positive lead wires 16 are connected to a first strain relief 20 .
- the thermal management device 10 also includes a pair of negative lead wires 18 connected to a second strain relief 22 .
- the thermal management device includes thermal fuses 21 on at least one pair of lead wires.
- the thermal fuses 21 may create an open circuit, such as by melting above a desired temperature.
- the thermal fuses 21 comprise a zinc metal fuse with a melting temperature of approximately 425 degrees Celsius.
- the thermal fuses 21 may be used to protect the thermal management device and related applications against thermal runaway.
- the thermal management device 10 may include a thermistor to measure temperature, and the measured temperature may be used to regulate or discontinue operation of the thermal management device when the measured temperature exceeds a desired limit.
- the thermal management device may include a positive temperature coefficient (“PTC”) thermistor to limit current flow above a determined temperature.
- PTC positive temperature coefficient
- Other fuses, circuit breakers, or current limiting devices also may be provided to protect the thermal management device and related application from overheating.
- the thermal management device 10 as illustrated in FIG. 1 is shown situated within a battery enclosure 24 .
- the battery enclosure 24 is a double walled enclosure surrounding the thermal management device and a plurality of energy storage cells (not shown).
- the thermal management device 10 is positioned above or below the energy storage cells to be heated.
- the thermal management device has multiple sections and may be interspersed with the energy storage cells to be heated.
- the battery enclosure 24 is electrically grounded and separated from the conductive elements of the thermal management device 10 .
- the battery enclosure 24 includes an aperture 26 through which the positive lead wires 16 and negative lead wires 18 of the thermal management device 10 extend.
- the aperture 26 of the battery enclosure 24 also provides an opening for the electrical connection to and from the energy storage cells.
- an aperture is provided for the lead wires and a separate aperture is provided for the power and control connections to the energy storage cells.
- the lead wires terminate in an electrical connector affixed to the battery enclosure 24 that provides a plug or receptacle for connecting to an external current source to power the thermal management device.
- retention straps 30 secure the thermal management device 10 within the battery enclosure 24 .
- the retention straps 30 contact the grounded battery enclosure 24 and are separated from the conductive elements including the plurality of heater legs 12 .
- the separation between the grounded elements, such as the battery enclosure 24 and retention straps 30 , and the energized elements, such as the heater legs, may be specified by applicable electrical safety codes and regulations for the voltages and currents employed in the system.
- a minimum clearance “A” is provided between the energized elements and any grounded material of at least 6 millimeters, at least 8 millimeters, or at least 10 millimeters depending upon the operating voltages of the thermal management device.
- the thermal management device 31 includes a housing 32 surrounding heating elements 36 and an insulator comprising a plurality of insulator panels 34 .
- the housing 32 includes an aperture 38 through which the lead wires 40 are routed.
- the housing 32 is formed of a material that is electrically non-conductive at least at temperatures at and above 200 degrees Celsius.
- the housing 32 is formed of an electrically conductive material and a non-conductive coating is applied such that the housing is electrically non-conductive at temperatures at and above 200 degrees Celsius.
- the operating temperature inside an energy storage device is approximately 300 degrees Celsius and the outer surfaces of housing 32 are electrically insulating at and above 300 degrees Celsius.
- the thickness of a thermal management device including housing 32 is no more than 15 millimeters, no more than 10 millimeters, or no more than 6 millimeters.
- the thermal management device is minimally bound by a rectangular parallelpiped boundary defined by three perpendicular axes, wherein a shortest of the axes is no more than 10 millimeters long.
- the housing 32 provides structural support for the thermal management device allowing the device to be handled and carried for installation.
- the housing 32 is provided with installation features, such as guide pins or mounting holes, to facilitate installation of a thermal management device in the desired application.
- FIG. 4 a partial view of a thermal management device is shown illustrating a heating element having a single heater leg configured in a spiral wound pattern around an insulator.
- the insulator is a planar material with a maximum use temperature of at least 200 degrees Celsius. In other embodiments, employing higher temperature heating elements, the insulator may have a maximum use temperature of at least 350 degrees Celsius or of at least 500 degrees Celsius.
- the insulator is formed of a sheet silicate insulator.
- One sheet silicate suitable for use as the insulator is mica, such as muscovite mica or phlogopite mica. In some applications, the insulator comprises phlogopite mica with a maximum use temperature of at least 800 degrees Celsius.
- the insulator is provided as one or more insulator panels, where each insulator panel is a mica sheet having a thickness of at least 0.40 millimeters.
- the insulator may be formed of silicon nitride. In yet other embodiments, the insulator may be a substrate of a thick film heater. The thickness of the planar insulator material may be selected to provide additional spacing between heating elements or to provide added rigidity to the thermal management device.
- One or more insulator panels may be utilized in the thermal management device.
- a plurality of mica sheets are secured in a stack by metal ribbon.
- multiple insulator panels are used to increase the thickness of insulation material to provide greater electrical or thermal insulation.
- multiple insulator panels are used to separate adjacent layers of heating elements in the thermal management device.
- a plurality of insulator panels are secured by rivets, by wire, or by non-conductive materials suitable for use at the operating temperature of the thermal management device.
- an insulator 50 that supports a heater leg 52 .
- the heater leg 52 may be an implementation of the heater legs 12 described previously in the present description.
- the insulator 50 includes notches 56 staggered on opposite edges of the insulator.
- the heater leg 52 is wound in a spiral configuration around the insulator 50 retained by the notches 56 .
- the portion of the heater leg extending on the underside of insulator 50 is illustrated by dashed lines 54 .
- the notches 56 are between 5 and 10 millimeters deep. The notches may be sized and spaced such that the heater leg 52 is supported in the notches, while the edge portions of the insulator 50 between the notches 56 retain sufficient strength to avoid breaking.
- the heater leg 52 is formed of a conductor that has a rectangular cross-section.
- a rectangular cross section conductor may achieve a lower profile and more evenly distribute forces applied to the insulator 50 by the heater leg 52 .
- a conductor or wire having a circular cross-section is used.
- the heater leg 52 provides resistive heating when current is passed through a conductor.
- the heat produced corresponds to the resistance of the conductor, which is determined by the length of the heater leg 52 , as well as, the current and voltage applied to the conductor.
- the spiral pattern winding of the heater leg 52 around the insulator 50 distributes the heat flux from the heater leg throughout the area containing the winding.
- the heater leg 52 may be configured in a variety of patterns on one or more planes to achieve the desired distribution of heat generation for the thermal management device.
- the spacing between successive windings of the heater leg 52 is selected based upon the operating voltage of the thermal management device.
- the thermal management device has an operating voltage of 56 volts.
- the thermal management device has an operating voltage of 575 volts.
- the spacing 58 between successive windings is at least 5% of the width 60 of the insulator 50 .
- the spacing 58 between successive windings is at least 20 millimeters and the width 60 of the insulator 50 is approximately 200 millimeters.
- the resistance of each heater leg is increased as compared to a single leg heater design.
- the resistance of a heater leg is increased by reducing the conductor cross section or by increasing the conductor length.
- an increased conductor length is achieved by providing additional windings around a larger insulator.
- the footprint of the thermal management device limits the dimensions of the insulator. Therefore to increase the conductor length, multiple insulators are stacked, with the heater legs wound around insulators at different levels in the stacked configuration. In this manner, the heating element of the thermal management device is selected to provide a specified thermal output, and the heater legs are configured on one or more layers to provide the resistance necessary to achieve the specified thermal output at the operating voltage and current of the thermal management device.
- a heating element 90 includes a heater leg 96 secured to a mica insulator 92 in a hook-and-ladder configuration. As shown, the heater leg 96 is secured to the edge of the insulator 92 by notches 94 . The heater leg 96 passes through notches 94 and is retained underneath the insulator 92 as illustrated by dashed lines 98 .
- both a spiral pattern winding and a hook-and-ladder configuration are used to secure a heater conductor to an insulator, such as by using a spiral pattern winding for at least a portion of the insulator while using a hook-and-ladder attachment adjacent at least one end of the insulator.
- the heating element 100 includes a first portion 102 of a heater leg supported on first insulator panel 104 .
- the heating element 100 also includes a second portion 106 of a heater leg supported on a second insulator panel 108 .
- a connecting portion 110 of the heater leg connects the first portion 102 and the second portion 106 of the heater leg and spans between the first insulator panel 104 and the second insulator panel 108 .
- the first and second insulator panels are supported on a third insulator panel, such that the first and second insulator panels lie in substantially the same plane.
- first insulator panel and second insulator panel are stacked vertically with a separation insulator panel in between and with the connecting portion 110 of the heater conductor extending around an edge of the separation insulator panel.
- the heater leg spans more than two insulator panels, each connected by a connecting portion of the heater leg.
- the spacing between successive windings is between (and including) 10 millimeters and 50 millimeters. In another embodiment, the spacing between successive windings is between (and including) 25 millimeters and 45 millimeters. In this manner, a heating element of the thermal management device is configurable into a variety of desired shapes and topologies to accommodate different operating environments and configurations.
- the heating element of the thermal management device includes two or more heater legs electrically connected in parallel to supply thermal energy. Having a plurality of heater legs connected in electrical parallel may increase the operational life of thermal management device.
- a thermal management device is utilized at less than 50%, or even less than 25% of its total heat output capability.
- a heating element with two or more heater legs may be capable of providing the necessary heat output even if one or more of the heater legs is damaged or becomes otherwise inoperative.
- a heating element with four heater legs may be capable of producing 25% of its total heat output with only one of the four heater legs operational.
- the expected operating life of a thermal management device is at least 10 years, and in other embodiments, the expected operating life is 20 years or greater. Over this operating lifespan, one or more heater legs may become inoperative, but the thermal management device may remain operational by maintaining sufficient heat output capability from the remaining functional heater leg or legs.
- the heating element 114 includes a first heater leg 118 and a second heater leg 120 .
- the first heater leg 118 and the second heater leg 120 are electrically connected in parallel, each providing one half of the device's heat output. Due to the parallel connection, if either heater leg fails, the other heater leg may remain operational, providing up to one half of the device's maximum heat output capability.
- the first heater leg 118 and second heater leg 120 are each wound in a spiral pattern around the insulator 116 .
- the heater legs are wound around more than one insulator.
- the first heater leg 118 is wound around a first insulator
- the second heater leg 120 is wound around a second insulator and each heater leg is connected to a common bus bar that provides the parallel electrical connection between the heater legs.
- heating element 122 includes an insulator 124 and four parallel heater legs 126 , 128 , 130 , 132 each wound in a spiral pattern around the insulator 124 .
- each heater leg provides approximately one fourth of the total heat output when all legs are functional.
- the heating element may still provide up to one fourth of the maximum heat output of the device, which, in some embodiments, is sufficient for the thermal management device to remain operational, thereby extending the useful life and reducing maintenance and repair costs.
- the heating element 134 includes an insulator 136 supporting a first heater leg 138 and a second heater leg 140 .
- the first heater leg 138 and the second heater leg 140 are supported on one side of the insulator 136 without being secured to the edges of the insulator 136 .
- the first heater leg 138 and the second heater leg 140 are woven through a series of holes (not shown) in the insulator 136 to secure the heater legs in place.
- first and second heater legs are placed on the insulator 136 and a second insulator (not shown) is placed on top of the heater legs and attached to the insulator 136 to retain the heater legs in the desired location.
- first heater leg 138 and the second heater leg 140 are connected in parallel by a first connection 142 and a second connection 144 , which may be bus bars or other electrical connections joining the heater legs in an electrically parallel configuration.
- a pair of positive lead wires 146 connect to the first connection 142
- a pair of negative lead wires 148 connect to the second connection 144 . In this manner, the thermal management device may remain operational even if one of each pair of lead wires were to be damaged or disconnected.
- a thermal management device includes a single heating element having a single leg disposed on a single layer.
- a thermal management device includes a single heater element having two or more legs on a single layer.
- a plurality of heating elements including a plurality of heater legs are disposed on one two or more layers within a thermal management device. Referring now to FIG. 10 , a portion of a thermal management device having multiple layers is illustrated. As shown, the thermal management device includes a plurality of insulators, including five insulator panels 72 , 74 , 76 , 78 , 80 in a stacked configuration. The insulator panels are secured by metal ribbon 82 extending through holes 84 provided in each of the insulator panels.
- the first insulator panel 74 and the second insulator panel 78 support spiral wound heater legs of the heating element of the thermal management device 70 .
- the third insulator panel 76 provides electrical insulation between the heater legs supported by the first insulator panel 74 and the second insulator panel 78
- the fourth insulator panel 72 and the fifth insulator panel 80 provide electrical insulation for the top and bottom surfaces of the thermal management device and protect the heater legs within.
- the metal ribbon 82 forms a retention device with a maximum use temperature of at least 500 degrees Celsius that secures insulator panels of the thermal management device to each other.
- other retention devices such as metal or non-conductive wire, may be used to secure a plurality of insulator panels to each other.
- rivets may be used to secure the plurality of insulator panels to each other.
- the plurality of insulator panels are flexibly connected such that the insulator panels may move relative to each other as the panels expand and contract with changes in temperature.
- a thermal management device 150 includes a first heating element 152 and a second heating element 154 .
- the first heating element 152 and the second heating element 154 each include a heater leg (not shown) wound in a spiral pattern around an insulator.
- the first heating element 152 and the second heating element 154 include two or more heater legs.
- the first heating element 152 and the second heating element 154 are separated by a separation insulator 156 .
- the separation insulator is a single sheet of mica.
- two or more sheets of mica are used to separate adjacent heating elements.
- the thermal management device 150 also includes a top insulator 158 and a bottom insulator 160 .
- the top insulator panel 158 and the bottom insulator panel 160 each are one or more sheets of mica insulation and are secured with metal ribbon.
- a thermal management device 162 includes a heating element with four heater legs 166 , where each heater leg is disposed on a separate layer of the thermal management device interposed with separation insulators 164 .
- the heater legs 166 are each connected to a common bus bar that is connected to lead wires (not shown) extending out of the thermal management device.
- the thermal management device 162 also includes a top insulator 170 and a bottom insulator 168 which bound the thermal management device and further protect the heater legs. As shown, each heater leg spans substantially the entire cross-section of the thermal management device, such as at least 90% of the cross-sectional area, providing a substantially uniform heat flux to the outer surfaces of the thermal management device.
- the heat flux at the bottom insulator 168 varies by no more than 25% from the average heat flux over the full surface of bottom insulator 168 . In another embodiment, the heat flux varies by no more than 20% from the average heat flux across the bottom insulator 168 when all heater legs are operational.
- the thermal management device 174 includes a top insulator 176 , a bottom insulator 178 , and a separation insulator 180 .
- a first heating element is disposed between the separation insulator 180 and the top insulator 176
- a second heating element is disposed between the separation insulator 180 and the bottom insulator 178 .
- Each heating element includes two heater legs electrically connected in parallel.
- the first heating element includes two heater legs 182 , 184 each disposed on approximately one half of the cross-section of the thermal management device 174 .
- the second heating element includes two heater legs 186 , 188 , each also disposed on approximately one half of the cross-section of the thermal management device. In this manner, each heating element provides heat flux over substantially the entire footprint of the thermal management device. More specifically, each heating element provides heat flux over at least 90% of either the top insulator 176 or the bottom insulator 178 of the thermal management device 174 .
- a thermal management device is configurable in various embodiments to provide the desired heat flux in a size and shape appropriate to the application.
- the heater leg of the heating element is a resistive wire formed of a suitable conductor. Thermal energy or heat is generated when a current is passed through the resistive wire.
- the length of the resistive wire or other resistive element is selected to provide a desired total resistance corresponding to the heat generation required to be produced by the thermal management device.
- the heater leg includes a resistive wire having a round or rectangular cross-section.
- a rectangular cross-section may provide a larger footprint for the resistive wire to contact the insulator reducing stress on the wire and the insulator.
- the heater leg is a nickel-chromium alloy resistive wire, such as nichrome, with a maximum use temperature of at least 1000 degrees Celsius.
- the nichrome may be Ni60Cr16Fe24, Ni80Cr20, or other nickel-chromium alloys.
- the nickel-chromium alloy is at least 75% nickel and, at least 15% chromium by weight, such as 80% nickel and 20% chromium by weight.
- the heater leg is an iron-chromium-aluminum alloy resistive wire with a maximum use temperature of at least 1000 degrees Celsius. In yet another embodiment, the heater leg is a nickel-iron alloy resistive wire with a maximum use temperature of at least 500 degrees Celsius. In yet another embodiment, the heater leg is a copper-nickel alloy resistive wire with a maximum use temperature of at least 500 degrees Celsius. In yet other embodiments, the heater leg is a resistive wire formed of an alloy containing essentially no carbon. In some embodiments, the heater leg has a high oxidation resistance. The heater leg may be a solid conductor or a braided conductor.
- embodiments of the thermal management device include lead wires configured to provide a parallel electrical connection between a current source and the heating element.
- the lead wires provide a parallel electrical connection between two or more electrically parallel heater legs of the heating element and the current source.
- the lead wires are formed of a conductive material, and may be either a solid conductor or a braided conductor.
- the lead wires are formed of a commercial grade pure nickel, such as nickel-200.
- nickel-200 is greater than 99.5% nickel.
- a lead wire formed of nickel-200 provides a high electrical conductivity and high corrosion resistance. Nickel-200 also has a maximum use temperature of at least 1400 degrees Celsius, allowing for prolonged use in high temperature applications.
- the lead wires are formed of nickel-201, a commercially pure wrought nickel with similar properties to nickel-200.
- nickel-201 may have a lower carbon content than nickel-200 and may resist carbon embrittlement from prolonged use at elevated temperatures.
- Nickel-201 also provides high electrical conductivity and high corrosion resistance.
- the lead wires are formed of copper, nickel-plated copper, aluminum, stainless steel, a nickel alloy, or other conductive material.
- the thermal management device includes a pair of positive lead wires connecting to a first pole of a heating element and a pair of negative lead wires connecting to a second pole of a heating element, such as illustrated in FIGS. 1 and 2 .
- the thermal management device includes two or more heating elements and Multiple pairs of lead wires, with each pair of lead wires connecting to one of the poles of one of the heating elements. In operation, each lead wire of a given pair supports approximately one half of the current supplied to the heating element. In other embodiments, more than two lead wires are provided for each pole of each heating element and each lead wires carries less than one half of the current supplied to the heating element.
- a maximum heat output is generated and a maximum current flows through the lead wires.
- the thermal management device may be operated at no more than 50%, or no more than 25% of its total capacity, with a corresponding reduction in the current required.
- each lead wire is designed to supply at least 50% of the total maximum current, and during subsequent operations, the thermal management device may remain operational even if one of the lead wires is damaged or otherwise inoperative. In this manner, the lead wires provide improved fault tolerance for the thermal management device and may extend the operational life of the thermal management device, thereby reducing costs for maintenance and repair.
- the lead wires of the thermal management device extend out of the body or main part of the thermal management device to connect to a current source to power the heating elements.
- the lead wires are provided with insulation to maintain electrical isolation between the lead wires and a housing or cover of the thermal management device.
- the lead wire insulation also provides mechanical protection to protect the lead wires against wear or damage as the lead wires are moved during installation or operation of the thermal management device. For example, various components of the thermal management device or surrounding application may expand and contract as a result of temperature changes over the lifespan of the thermal management device, causing movement of the lead wires relative to other components in the system.
- the lead wire insulator provides mechanical protection to the conductor during movement of the lead wire.
- the lead wires are insulated with an electrically insulating material having a maximum use temperature of at least 400 degrees Celsius.
- the lead wires are insulated with an abrasion resistant material.
- the lead wire insulation is a polytetrafluoroethylene (PTFE) (e.g., Teflon® brand) coated fiberglass insulation.
- PTFE is a synthetic fluoropolymer of tetrafluoroethylene that finds numerous applications. PTFE is most well known by the DuPont brand name Teflon.
- the lead wire insulation is a mica-PTFE-fiberglass insulation (“MTG”).
- MTG insulation includes a combination of fiberglass, PTFE tape, and phlogopite mica tape.
- the lead wires are protected by a metal braided mesh covering.
- the lead wire insulation is a polymide insulation, phenolics insulation, cement insulation, ceramic insulation, or combinations thereof.
- the temperature within a battery enclosure is approximately 300 degrees Celsius and the current flow through the lead wires may increase the temperature of the lead wire insulation up to 400 degrees Celsius.
- the lead wire insulation has a maximum use temperature of at least 400 degrees Celsius.
- the current flow through the lead wire is limited such that the maximum use temperature of the lead wire insulation is not exceeded during operation of the thermal management device.
- the thermal management device may also have one or more strain reliefs provided for the parallel lead wires.
- mechanical failure of lead wire connections have rendered battery heaters inoperative, and as a result, required replacement or repair of rechargeable battery systems.
- Providing one or more strain reliefs for the lead wires may thus improve the reliability of the thermal management device, extending the operational life and reducing maintenance and repair costs of a system employing the thermal management device.
- a strain relief block 200 is attached to the insulator 202 , such as a mica sheet.
- the strain relief block 200 is attached to the insulator 202 by rivets 204 .
- the strain relief block 200 is attached to the insulator 202 by other mechanical or adhesive connections compatible with the operating temperature of the thermal management device.
- the strain relief block 200 is positioned so as to reduce the length of the lead wires extending out of a housing for the thermal management device. As shown, a lead wire 206 having lead wire insulation 208 extends towards the strain relief block 200 .
- a portion of the conductor of the lead wire 206 is exposed and mechanically secured to the strain relief block 200 at first connection 210 .
- a portion of the conductor of a heater leg 212 is mechanically secured to the strain relief block 200 at a second connection 214 .
- the lead wire 206 and the heater leg 212 are electrically connected at the strain relief block 200 .
- the strain relief block 200 provides an electrical connection between the first connection 210 and the second connection 214 to transfer current from the lead wire 206 to the heater leg 212 .
- the strain relief block 200 provides a connection for a single heater leg 212 and a single lead wire 206 , such as shown in FIG. 14 .
- a strain relief block may include a plurality of first connections each configured to connect one or more lead wires, and a plurality of second connections each configured to connect one or more heater legs.
- two or more strain relief blocks may be provided to support the lead wires and heater legs of the thermal management device. Connecting the lead wire 206 and the heater leg 212 to the strain relief block 200 reduces stress on the electrical connection between the lead wire and the heater leg as the lead wires are routed through a housing, or manipulated during assembly or installation of the thermal management device.
- a strain relief connection is illustrated, where the lead wires are connected to the strain relief by a weld connection and by a mechanical connection.
- a lead wire 220 is connected to a strain relief pad 222 by a weld connection 224 .
- the weld connection includes a brazing or a solder connection when the operating temperature of the thermal management device is below the melting temperature of a connection formed using those technologies.
- temperatures near the weld connection may reach 800 degrees Celsius and a welded joint with a melt temperature of at least 800 degrees Celsius is utilized.
- the lead wire 220 is also secured to the strain relief pad 222 by mechanical connections 226 on either side of the weld connection 224 .
- the mechanical connections 226 maintain the electrical connection between the lead wire 220 and a conductive portion of the strain relief pad 222 .
- the weld connection 224 may connect the lead wire 220 to a conductor of a heater leg and may or may not form a welded connection to the strain relief pad 222 .
- the mechanical connection includes a twist tie.
- the mechanical connection includes folding or wrapping the lead wire around a portion of the strain relief pad 222 . The mechanical connection may be selected based on the operating temperature of the thermal management device. For some applications polymer tapes are utilized.
- the mechanical connection 226 includes rivets used to secure the lead wire 220 to the strain relief pad 222 .
- the strain relief pad 222 is secured to the insulator 230 by rivets 232 , 234 .
- the rivets 232 , 234 securing the strain relief pad 222 to the insulator 230 are positioned between the weld connection 224 and the mechanical connections 226 to improve the distribution of forces applied to the lead wire.
- the thermal management device is manufactured by securing a lead wire to the strain relief by welding prior to securing the mechanical connections on either side of the welded connection to minimize stress on the lead wire during installation.
- a lead wire 240 is welded to a conductor of a heater leg 242 by a weld 244 .
- the weld 244 establishes both an electrical and mechanical connection between the lead wire 240 and the heater leg 242 and avoids the introduction of oxides between the conductors.
- the strain relief also includes a crimp tube 248 .
- the lead wire 240 and heater leg 242 are positioned within the crimp tube 248 , and all three components are welded together as illustrated by the weld 244 .
- crimp connections 246 are provided on either side of the weld 244 to provide mechanical support to the lead wire and heater leg.
- the crimp connections 246 absorb and dissipate stresses resulting from movement of the lead wire 240 , further protecting the weld connection.
- a combination of mechanical connections such as twisted, tied, folded, crimped, or riveted, are used to secure the lead wire and heater leg to the strain relief.
- the thermal management device 250 includes a first insulator 258 , and a second insulator 256 .
- One or more heating elements are disposed between the first and second insulators as previously discussed.
- the first insulator 258 is a center panel within a generally symmetric arrangement of insulator panels and heating elements are provided both above and below the center panel.
- a pair of positive lead wires 252 may extend from a first strain relief block 262 secured to the first insulator 258 , where the positive lead wires are electrically connected to at least one heater leg at connection 264 .
- a pair of negative lead wires 254 may extend from a second strain relief block 266 secured to the first insulator, where the negative lead wires are electrically connected to at least one heater leg at connection 268 .
- the strain relief blocks are not utilized and the lead wires may be connected to the heater legs by other methods.
- the first insulator 258 of the thermal management device 250 also includes a plurality of apertures 260 configured for routing the pair of positive lead wires 252 and the pair of negative lead wires 254 . As shown, the lead wires may be laced through the apertures 260 extending on alternating sides of the insulator between adjacent apertures.
- the positive lead wires 252 are laced through apertures separate from the apertures used for negative lead wires 254 .
- the apertures 260 are illustrated in a generally circular configuration, apertures of other shapes may also be used.
- the first insulator 258 having apertures 260 provides a strain relief for the lead wires. If tension is applied to the lead wires, the resulting stresses may be at least partially transferred to the first insulator 258 as the lead wires pull against the edges of the apertures 260 . In this manner, the electrical and mechanical connections of the lead wires are further protected against breakage or other damage.
- an insulator 270 is illustrated with another embodiment of a strain relief for the lead wires of the thermal management device.
- the insulator 270 supports one or more heater legs. A portion of a heater leg 282 is illustrated connected to a lead wire 275 by weld 280 .
- the insulator 270 is provided with a first channel 272 extending through the insulator. The first channel 272 is configured to receive a first pair of lead wires 275 , 276 .
- the insulator 270 also includes a second channel 274 extending through the insulator panel. The second channel 274 is configured to receive a second pair of lead wires 278 .
- Each one of the first pair of lead wires 275 , 276 is disposed within a portion of the first channel 272 .
- the first channel 272 is substantially U-shaped and each one of the pair of first lead wires 275 , 276 is disposed in one segment of the first channel 272 .
- the first channel 272 may include two sections that are unconnected.
- the width of the first channel 272 is sized to accommodate the diameter of the lead wires 275 , 276 .
- the width of the first channel 272 is substantially the same dimension as the lead wire diameter, such as between 95% and 105% of the lead wire diameter. In another embodiment, the width of the first channel 272 is between 98% and 102% of the lead wire diameter.
- the width of the first channel 272 is substantially equal to the diameter of the lead wires 275 , 276 such that each lead wire is mechanically secured in the channel due to interference between the lead wire insulation and the sides of the channel.
- the first channel 272 provides a strain relief as forces on the lead wire are at least partially transmitted to the insulator 270 .
- the lead wires 275 , 276 are secured to the heater leg 282 by welds, such as the weld 280 illustrated for the lead wire 275 .
- the second pair of lead wires 278 are retained and strain-relieved by second channel 274 , and connected to a heater leg by weld 284 .
- the weld 280 is disposed within the first channel 272 such that the weld does not increase the overall thickness of the thermal management device.
- the overall thickness of the thermal management device is equal to the thickness of an upper and lower insulation panel plus the diameter of the lead wire disposed between the upper and lower insulation panels in the first channel 272 .
- the first pair of lead wires 276 extend from the first channel through a first hole 286 provided in a bottom insulator 290 .
- the second pair of lead wires 278 extend from the second channel through a second hole 288 provided in the bottom insulator 290 .
- the first hole 286 and the second hole 288 may be provided in a top insulator when it is desired to route the lead wires out the top side of the thermal management device.
- the first hole 286 and the second hole 288 may be provided on opposite sides of the thermal management device when it is desired to route the positive and negative lead wires on opposite sides of the thermal management device.
- one hole may be provided for each of the lead wires to accommodate other configurations and applications, or a single hole may be provided for all lead wires.
- the lead wires are routed at approximately a 90° angle from the channel of an interior insulator through the hole in an exterior insulator, for providing additional strain relief.
- the interior and exterior insulators may be joined by metal ribbon 292 such that the lead wires are secured in the channel of the interior insulator.
- the strain relief provided by the channel and hole may be used in connection with one or more of the strain relief systems previously discussed.
- the thermal management device 300 includes a heating element 310 disposed within a housing 302 .
- the housing 302 has a top surface and a bottom surface (not shown).
- the thermal management device 300 is positioned within a battery enclosure above a plurality of energy storage cells such that heat flux across the bottom surface of the housing 302 heats the energy storage cells to a desired operating temperature and maintains the energy storage cells at the desired operating temperature as needed throughout the lifespan of the battery system.
- the heating element 310 includes a first heater leg 312 and a second heater leg 314 .
- the first heater leg 312 and the second heater leg 314 are electrically connected in parallel and each is connected to a first strain relief block 322 and a second strain relief block 324 .
- the first strain relief block 322 and the second strain relief block 324 are each connected to an insulator 316 (e.g., a mica insulator panel) about which the first and second heater legs are wound in a spiral pattern.
- a pair of positive lead wires 318 are connected to the first strain relief block 322 , and extend out of the housing 302 through an aperture 304 .
- a pair of negative lead wires 320 are connected to the second strain relief block 324 and extend out of the housing 302 through the aperture 306 .
- the thermal management device 300 is configured to generate heat for a battery system by passing current through positive lead wires; first and second heater legs, and negative lead wires. Additionally, the thermal management device 300 may remain operational in the event of a failure of one lead wire of each pair, or one of the first and second heater legs.
- the first heater leg 312 and the second heater leg 314 are each configured to provide substantially uniform heat flux over the top surface and/or bottom surface of the thermal management device 300 .
- a substantially uniform heat flux over a surface is defined as a local heat flux that varies by no more than 25% from the average heat flux over the footprint defined by the heater legs of the thermal management device.
- a substantially uniform heat flux over a surface is defined as a local heat flux that varies by no more than 20% from the average heat flux over the footprint defined by the heater legs of the thermal management device.
- a substantially uniform heat flux is defined as a local heat flux in any one square inch region that varies by no more than 25% from the average heat flux over the footprint defined by one leg of a heating element of the thermal management device.
- each heating element is configured to provide uniform heat flux over at least 20% of one surface of the device.
- each heater leg is configured to provide uniform heat flux over at last 20% of one surface of the thermal management device.
- a thermal management device configured to provide a substantially uniform heat flux may result in a more even heating of the energy storage cells or other structures being heated.
- a thermal management device having a plurality of heater legs with each heater leg configured to provide substantially uniform heat flux over at least 90% of the surface, if a heater leg is damaged or become inoperative, the remaining operational heater leg(s) may still provide a substantially uniform heat flux to the energy storage cells or other structuring being heated.
- the thermal management device 350 has a heating element including a plurality of heater legs each supported on an insulator within a housing 352 .
- a first heater leg 354 provides a first heating region corresponding to a portion of the area to be heated
- a second heater leg 356 provides a second heating region corresponding to a different portion of the area to be heated.
- the first heating region corresponds to an interior portion of an energy storage device
- the second heating region corresponds to a perimeter region of an energy storage device with a greater thermal loss than the interior region of the energy storage device.
- the thermal management device may be configured to provide greater heat flux in the regions where the structure has the greater heat loss.
- an energy storage device may have greater heat loss around the perimeter of the device, resulting in energy storage cells near the perimeter having a lower temperature than energy storage cells in an interior portion of the device.
- the thermal management device 350 is configured to at least partially compensate for the uneven heat distribution by providing increased heat flux to those regions where the energy storage device experiences greater thermal losses.
- the first heater leg 354 provides a first heating region, where the first heating region corresponds to (e.g., is primarily configured to impart thermal energy to) an interior portion of an energy storage device.
- the second heater leg 356 provides a second heating region, where the second heating region corresponds to at least a portion of a perimeter of an energy storage device having greater heat loss than the interior portion.
- the first and second heater legs are configured such that the second heating region has a heat flux at least 25% greater than the heat flux of the first region.
- the heat flux of the second heating region is between (and including) 10% and 25% greater than the heat flux of the first heating region.
- the difference in the desired heat flux between the first and second heating regions may be selected based on thermal characteristics of the specific structure or application to be heated by the thermal management device.
- the thermal management device 350 may also include a third heater leg 358 , a fourth heater leg 360 , and a fifth heater leg 362 extending substantially around the perimeter of the thermal management device.
- the plurality of heater legs define one or more additional heating regions providing a heat flux selected to achieve a substantially uniform temperature among the energy storage cells of an energy storage device.
- an energy storage device may have a temperature gradient across the energy storage cells of the device. Such a temperature gradient may result in an energy storage cell thermal profile 370 along a cross section of the energy storage device, such as illustrated in FIG. 22 , where the relative temperature of the energy storage cells is indicated by the length of the bars in the thermal profile 370 . As indicated by the thermal profile 370 , the cells near the perimeter of the energy storage device may have a lower temperature because of heat loss 372 from the sides of an enclosure. In contrast, the cells in the interior portions 374 of the energy storage device may have a relatively higher temperature as indicated.
- a thermal management device 380 may be provided having a non-uniform heat flux profile 382 , such as illustrated in FIG. 23 .
- the amount of heat flux from the thermal management device is illustrated by the length of the arrows of the heat flux profile 382 .
- the non-uniform heat flux profile 382 includes regions of relatively greater heat flux corresponding to the regions near the perimeter of the energy storage device where thermal loss may be greatest.
- the non-uniform heat flux profile 382 may also have regions of lower heat flux corresponding to interior portions of the energy storage device where thermal loss is reduced.
- the heat flux profile 382 may have a gradual transition as illustrated or may include one or more discrete levels.
- the heat flux between a first region, such as near the perimeter may be at least 15%, at least 25%, or at least 50% greater than the heat flux in a second region, such as an interior portion.
- the thermal management device has the heat flux profile 382 illustrated in FIG. 23 that corresponds the thermal profile 370 of the energy storage device illustrated in FIG. 22 .
- an energy storage device may achieve a uniform cell temperature illustrated by thermal profile 390 , even with heat loss 392 from the perimeter of the device.
- the temperature of energy storage cells in the interior portion 394 is maintained substantially the same as the temperate of the energy storage cells adjacent the perimeter where the heat loss 392 is greater.
- the configuration of heater legs, or the position of the heater legs or heating elements may be adjusted to achieve the desired heat flux profile.
- the thermal management device may include two or more independently controllable heating elements and a control system may be provided to operate the heating elements to achieve the desired heat flux profile.
- FIGS. 25 and 26 show an embodiment of an energy storage device 400 having a thermal management device 402 .
- the energy storage device 400 includes the thermal management device 402 and a plurality of energy storage cells 404 disposed within a battery enclosure 406 .
- the thermal management device 402 is positioned above the cells 404 . In other embodiments however, the thermal management device is positioned below or between the cells. In yet another embodiment, two or more thermal management devices are provided within the battery enclosure to achieve the desired heating of the cells.
- the cells are sodium-metal-halide cells having an operating temperature of approximately 300 degrees Celsius.
- the thermal management device 402 provides a maximum heat output to heat the cells to the desired operating temperature. The heat output is then reduced or discontinued as necessary to maintain the cells within a desired operating range, such as between (and including) 280 degrees Celsius and 320 degrees Celsius.
- the battery enclosure 406 includes a lead wire aperture 408 for the lead wires of the thermal management device to exit the battery enclosure.
- the battery enclosure also includes a power connector 410 configured to connect the power and control signals from the energy storage cells and battery management system.
- the battery enclosure also includes a pair of cooling ports 412 configured to transfer cooling fluid into and out of the battery enclosure to cool the energy storage cells 404 as needed during operation.
- the lead wire aperture, power connector, and ports are located on a first side 422 of the battery enclosure that is opposite a second side 424 of the battery enclosure 406 .
- the energy storage device is illustrated with the heater legs of thermal management device 402 exposed.
- the thermal management device 402 has four heater legs 420 , each wound in a spiral pattern around a mica panel or other insulator.
- the four heater legs 420 are electrically connected in parallel.
- the heater legs 420 are oriented to extend generally between the first side 422 and the second side 424 of the energy storage device.
- the first side 422 of the energy storage device 400 has a greater thermal loss than the second side 424 .
- the presence of lead wire aperture 408 , power connector 410 , and cooling ports 412 extending through first side 422 may reduce the thermal resistance of first side 422 of the battery enclosure 406 , thereby increasing the thermal loss through the first side.
- the orientation of the energy storage cells 404 within battery enclosure 406 may result in a disproportionate thermal loss on one side of the energy storage device.
- the energy storage device 400 has a first axis 426 extending between opposing sides, such as first side 422 and second side 424 .
- the energy storage device 400 also has a second axis 428 perpendicular to the first axis 426 .
- the temperature gradient across the energy storage cells 404 is greater along the first axis 426 than the temperature gradient across the energy storage cells 404 along the second axis 428 .
- the heater legs of the heating element may be aligned with the first axis 426 . When all four heater legs are operational, the heat flux from the thermal management device to the energy storage cells is substantially uniform and the variation in temperature among the energy storage cells is reduced.
- having the heater legs aligned with the first axis 426 , between the first side 422 and the second side 424 may maintain a more uniform temperature distribution among the energy storage cells even when one or more of the heater legs is inoperative.
- a simulated thermal profile in degrees Kelvin is illustrated for the cells of an energy storage device having a thermal management device.
- the energy storage cell temperature gradient is predicted to be greater along the first axis 426 than along the second axis 428 .
- the maximum simulated temperature of the energy storage cells is 582 degrees Kelvin, while the minimum simulated cell temperature is 558 degrees Kelvin, resulting in a total variation in cell temperature of 24 degrees Kelvin, which may be within the acceptable range for the selected cell chemistry.
- the thermal management device 500 comprising a pair of heating elements in a stacked arrangement.
- the thermal management device 500 includes a first heating element 504 connected to a positive lead wire 506 and a negative lead wire 508 .
- the thermal management device also includes a second heating element 516 connected to a positive lead wire 512 and a negative lead wire 514 .
- the first heating element 504 is operationally connected and used during operation of the thermal management device, while the second heating element 516 is not connected and is provided as a spare or backup heating element in the event of a failure of the first heating element. In this manner, the second heating element 516 provides a built in replacement or substitute for the first heating element 504 .
- the first heating element 504 and the second heating element 516 are each capable of providing the necessary heat flux to an application such that only one heating element is required for operation. In some applications, replacement of the thermal management device may not be feasible and having a spare heating element may provide a cost effective means of returning an application to a functional state after failure of a heating element.
- a thermal management device provides improved reliability, and more uniform cell temperatures as compared to devices of the prior art.
- the thermal management device may achieve an operational life span matching or exceeding the twenty year life expectancy of certain rechargeable battery systems thereby reducing maintenance and repair costs.
- the terms “may” and “may be” indicate a possibility of an occurrence within a set of circumstances; a possession of a specified property, characteristic or function; and/or qualify another verb by expressing one or more of an ability, capability, or possibility associated with the qualified verb. Accordingly, usage of “may” and “may be” indicates that a modified term is apparently appropriate, capable, or suitable for an indicated capacity, function, or usage, while taking into account that in some circumstances the modified term may sometimes not be appropriate, capable, or suitable. For example, in some circumstances an event or capacity can be expected, while in other circumstances the event or capacity cannot occur—this distinction is captured by the terms “may” and “may be.”
Abstract
A thermal management device is presently disclosed. The device includes a plurality of insulator panels with a maximum use temperature of at least 500 degrees Celsius, and a heating element having at least two heater legs electrically connected in parallel, each heater leg contacting at least one of the insulator panels, and lead wires configured to provide a parallel electrical connection between the heater legs and a current source. Also disclosed is a thermal management device having an insulator and a heating element, where each of the electrically parallel heater legs is configured to provide substantially uniform heat flux over at least one surface of the device. Also disclosed is an energy storage device that includes a plurality of energy storage cells, and a thermal management device configured to supply thermal energy to the cells.
Description
- 1. Technical Field
- The subject matter disclosed herein relates to thermal management devices, and more particularly, to thermal management devices for use with rechargeable batteries.
- 2. Discussion of Art
- Rechargeable batteries may have challenges in thermal management and thermal regulation, particularly as the life span of the rechargeable energy storage cells increases. Premature failure of a thermal management device renders a rechargeable battery inoperative, increasing maintenance and repair costs and reducing the effectiveness of the battery system. These challenges with existing thermal management devices affect the efficiency of the battery operations and also the efficiency and operating costs of the system or systems supported by the battery.
- It may be desirable to have a thermal management device that differs from those that are currently available.
- Presently disclosed is a thermal management device. In one embodiment, the thermal management device has an insulator with a maximum use temperature greater than about 200 degrees Celsius, and a heating element with at least one heater leg. The heater leg contacts the insulator and is configured to supply thermal energy, such as to a rechargeable energy storage cell. The heating element has lead wires configured to provide a parallel electrical connection between the at least one heater leg and a current source for the thermal management device.
- In another embodiment, a thermal management device includes a plurality of insulator panels with a maximum use temperature of at least 500 degrees Celsius, and a heating element comprising at least two heater legs electrically connected in parallel, where each heater leg contacts at least one of the insulator panels and is configured to supply thermal energy, such as to a rechargeable energy storage cell. The heating element has lead wires configured to provide a parallel electrical connection between the heater legs and a current source.
- In another embodiment, a thermal management device includes an insulator with a maximum use temperature greater than about 500 degrees Celsius, and a heating element with at least two heater legs electrically connected in parallel. The heater legs contact the insulator and are configured to supply thermal energy to a plurality of energy storage cells. In one embodiment, each of the parallel heater legs is configured to provide substantially uniform heat flux over at least one surface of the device.
- Also disclosed is an energy storage device. In one embodiment, the energy storage device includes a plurality of energy storage cells having an operating temperature of at least 250 degrees Celsius, and a thermal management device. The thermal management device has an insulator with a maximum use temperature of at least 500 degrees Celsius, and a heating element contacting the insulator and having a plurality of heater legs electrically connected in parallel. The heating element is configured to supply thermal energy to the plurality of energy storage cells. In one embodiment, the heating element includes lead wires configured to provide a parallel electrical connection between the heater legs and a current source.
- Reference is made to the accompanying drawings in which particular embodiments and further benefits of the invention are illustrated as described in more detail in the description below, in which:
-
FIG. 1 is a schematic view of a thermal management device: -
FIG. 2 is a schematic view of a thermal management device in a battery enclosure: -
FIG. 3 is a cross-section view of a thermal management device having a housing; -
FIG. 4 is a perspective view of a first heating element; -
FIG. 5 is a top view of a second heating element; -
FIG. 6 is a top view of third heating element; -
FIG. 7 is a top view of fourth heating element; -
FIG. 8 is a top view of fifth heating element; -
FIG. 9 is a top view of sixth heating element; -
FIG. 10 is a perspective view of a portion of a thermal management device; -
FIG. 11 is a side view of a second thermal management device; -
FIG. 12 is a side view of a third thermal management device; -
FIG. 13 is a side view of a fourth thermal management device; -
FIG. 14 is a top view of a strain relief; -
FIG. 15 is a cross-section view of a strain relief; -
FIG. 16 is a cross-section view of another strain relief; -
FIG. 17 is a top view of a thermal management device with a strain relief; -
FIG. 18 is a view of a thermal management device with a strain relief with the bottom insulator removed; -
FIG. 19 is a bottom view of the thermal management device ofFIG. 18 with the bottom insulator installed; -
FIG. 20 is a top view of another thermal management device; -
FIG. 21 is a top view of another thermal management device; -
FIG. 22 is a thermal profile of an energy storage device; -
FIG. 23 is a heat flux profile of a thermal management device; -
FIG. 24 is a thermal profile of an energy storage device with substantially uniform cell temperature; -
FIG. 25 is a cross-section of an energy storage device having a thermal management device; -
FIG. 26 is a perspective view of an energy storage device with the top cover removed; -
FIG. 27 is a simulated thermal profile of a battery having a thermal management device; and -
FIG. 28 is a schematic view of another thermal management device in a battery enclosure. - The subject matter disclosed herein relates to a thermal management device, and an energy storage device, such as a rechargeable battery system that includes a thermal management device. Referring generally to
FIGS. 1 through 28 , embodiments of a thermal management device and an energy storage device having a thermal management device are disclosed. - In various embodiments, a thermal management device includes an insulator, a heating element, and lead wires configured to provide a parallel electrical connection between the heating element and a current source. The heating element may have one or more heater legs electrically connected in parallel, where the heater legs contact the insulator and are configured to supply thermal energy to a structure to be heated by the thermal management device, such as an energy storage cell (electrochemical cell) of a rechargeable battery. The insulator may be a sheet silicate or other insulating material capable of supporting the heating element at the operating temperature of the thermal management device. The lead wires are configured to provide a parallel electrical connection between the heating element and a current source. When the thermal management device is utilized in an energy storage device, such as a rechargeable battery system, the current source may be the same current source used to charge the rechargeable battery, or it may be a separate current source.
- Referring to
FIG. 1 , an electrical configuration of one embodiment of a thermal management device is illustrated in schematic form. As shown, thethermal management device 10 has a heating element with fourheater legs 12 electrically connected in parallel. In one embodiment, theheater legs 12 are connected tobus bars 14, but in other embodiments, theheater legs 12 may be connected directly to each other to form the electrically parallel connection. In some embodiments, the plurality of heater legs improves the fault tolerance of the thermal management device, which may continue to operate even if one or more of the heater legs becomes inoperative. As shown, thethermal management device 10 also includes a pair of positivelead wires 16 providing an electrical connection to the heating element. Thepositive lead wires 16 are connected to afirst strain relief 20. Thethermal management device 10 also includes a pair of negativelead wires 18 connected to asecond strain relief 22. In one embodiment, the thermal management device includes thermal fuses 21 on at least one pair of lead wires. The thermal fuses 21 may create an open circuit, such as by melting above a desired temperature. In one embodiment, the thermal fuses 21 comprise a zinc metal fuse with a melting temperature of approximately 425 degrees Celsius. The thermal fuses 21 may be used to protect the thermal management device and related applications against thermal runaway. In other embodiments, thethermal management device 10 may include a thermistor to measure temperature, and the measured temperature may be used to regulate or discontinue operation of the thermal management device when the measured temperature exceeds a desired limit. In yet another embodiment, the thermal management device may include a positive temperature coefficient (“PTC”) thermistor to limit current flow above a determined temperature. Other fuses, circuit breakers, or current limiting devices also may be provided to protect the thermal management device and related application from overheating. - Referring to
FIG. 2 , thethermal management device 10 as illustrated inFIG. 1 is shown situated within abattery enclosure 24. In one embodiment, thebattery enclosure 24 is a double walled enclosure surrounding the thermal management device and a plurality of energy storage cells (not shown). In various configurations, thethermal management device 10 is positioned above or below the energy storage cells to be heated. In other embodiments, the thermal management device has multiple sections and may be interspersed with the energy storage cells to be heated. In many applications thebattery enclosure 24 is electrically grounded and separated from the conductive elements of thethermal management device 10. As illustrated, thebattery enclosure 24 includes anaperture 26 through which thepositive lead wires 16 and negativelead wires 18 of thethermal management device 10 extend. In one embodiment, theaperture 26 of thebattery enclosure 24 also provides an opening for the electrical connection to and from the energy storage cells. In other embodiments, an aperture is provided for the lead wires and a separate aperture is provided for the power and control connections to the energy storage cells. In yet another embodiment, the lead wires terminate in an electrical connector affixed to thebattery enclosure 24 that provides a plug or receptacle for connecting to an external current source to power the thermal management device. - In an embodiment, retention straps 30 secure the
thermal management device 10 within thebattery enclosure 24. The retention straps 30 contact the groundedbattery enclosure 24 and are separated from the conductive elements including the plurality ofheater legs 12. The separation between the grounded elements, such as thebattery enclosure 24 andretention straps 30, and the energized elements, such as the heater legs, may be specified by applicable electrical safety codes and regulations for the voltages and currents employed in the system. In various embodiments, a minimum clearance “A” is provided between the energized elements and any grounded material of at least 6 millimeters, at least 8 millimeters, or at least 10 millimeters depending upon the operating voltages of the thermal management device. - Referring now to
FIG. 3 , in another embodiment, thethermal management device 31 includes ahousing 32 surroundingheating elements 36 and an insulator comprising a plurality ofinsulator panels 34. As illustrated, thehousing 32 includes anaperture 38 through which thelead wires 40 are routed. In one embodiment, thehousing 32 is formed of a material that is electrically non-conductive at least at temperatures at and above 200 degrees Celsius. In another embodiment, thehousing 32 is formed of an electrically conductive material and a non-conductive coating is applied such that the housing is electrically non-conductive at temperatures at and above 200 degrees Celsius. In one embodiment, the operating temperature inside an energy storage device is approximately 300 degrees Celsius and the outer surfaces ofhousing 32 are electrically insulating at and above 300 degrees Celsius. The overall dimensions of the thermal management device may be optimized for specific applications. In various embodiments, the thickness of a thermal managementdevice including housing 32 is no more than 15 millimeters, no more than 10 millimeters, or no more than 6 millimeters. In one embodiment, the thermal management device is minimally bound by a rectangular parallelpiped boundary defined by three perpendicular axes, wherein a shortest of the axes is no more than 10 millimeters long. In another embodiment, thehousing 32 provides structural support for the thermal management device allowing the device to be handled and carried for installation. In yet another embodiment, thehousing 32 is provided with installation features, such as guide pins or mounting holes, to facilitate installation of a thermal management device in the desired application. - Referring now to
FIG. 4 , a partial view of a thermal management device is shown illustrating a heating element having a single heater leg configured in a spiral wound pattern around an insulator. - In one embodiment, the insulator is a planar material with a maximum use temperature of at least 200 degrees Celsius. In other embodiments, employing higher temperature heating elements, the insulator may have a maximum use temperature of at least 350 degrees Celsius or of at least 500 degrees Celsius. In one embodiment, the insulator is formed of a sheet silicate insulator. One sheet silicate suitable for use as the insulator is mica, such as muscovite mica or phlogopite mica. In some applications, the insulator comprises phlogopite mica with a maximum use temperature of at least 800 degrees Celsius. In some embodiments, the insulator is provided as one or more insulator panels, where each insulator panel is a mica sheet having a thickness of at least 0.40 millimeters. In other embodiments, the insulator may be formed of silicon nitride. In yet other embodiments, the insulator may be a substrate of a thick film heater. The thickness of the planar insulator material may be selected to provide additional spacing between heating elements or to provide added rigidity to the thermal management device.
- One or more insulator panels may be utilized in the thermal management device. In one embodiment, a plurality of mica sheets are secured in a stack by metal ribbon. In some embodiments, multiple insulator panels are used to increase the thickness of insulation material to provide greater electrical or thermal insulation. In other embodiments, multiple insulator panels are used to separate adjacent layers of heating elements in the thermal management device. In another embodiment, a plurality of insulator panels are secured by rivets, by wire, or by non-conductive materials suitable for use at the operating temperature of the thermal management device.
- As shown in the embodiment of
FIG. 4 , aninsulator 50 is provided that supports aheater leg 52. Theheater leg 52 may be an implementation of theheater legs 12 described previously in the present description. Theinsulator 50 includesnotches 56 staggered on opposite edges of the insulator. Theheater leg 52 is wound in a spiral configuration around theinsulator 50 retained by thenotches 56. The portion of the heater leg extending on the underside ofinsulator 50 is illustrated by dashedlines 54. In one embodiment, thenotches 56 are between 5 and 10 millimeters deep. The notches may be sized and spaced such that theheater leg 52 is supported in the notches, while the edge portions of theinsulator 50 between thenotches 56 retain sufficient strength to avoid breaking. In one embodiment, theheater leg 52 is formed of a conductor that has a rectangular cross-section. A rectangular cross section conductor may achieve a lower profile and more evenly distribute forces applied to theinsulator 50 by theheater leg 52. In alternative embodiments, a conductor or wire having a circular cross-section is used. - The
heater leg 52 provides resistive heating when current is passed through a conductor. The heat produced corresponds to the resistance of the conductor, which is determined by the length of theheater leg 52, as well as, the current and voltage applied to the conductor. The spiral pattern winding of theheater leg 52 around theinsulator 50 distributes the heat flux from the heater leg throughout the area containing the winding. As noted below, theheater leg 52 may be configured in a variety of patterns on one or more planes to achieve the desired distribution of heat generation for the thermal management device. - In one embodiment, the spacing between successive windings of the
heater leg 52 is selected based upon the operating voltage of the thermal management device. In one embodiment, the thermal management device has an operating voltage of 56 volts. In another embodiment, the thermal management device has an operating voltage of 575 volts. In one embodiment, the spacing 58 between successive windings is at least 5% of thewidth 60 of theinsulator 50. In another embodiment, the spacing 58 between successive windings is at least 20 millimeters and thewidth 60 of theinsulator 50 is approximately 200 millimeters. - To maintain a given electrical resistance for the heating element while connecting multiple heater legs in parallel, the resistance of each heater leg is increased as compared to a single leg heater design. The resistance of a heater leg is increased by reducing the conductor cross section or by increasing the conductor length. In one embodiment, an increased conductor length is achieved by providing additional windings around a larger insulator. In other embodiments, the footprint of the thermal management device limits the dimensions of the insulator. Therefore to increase the conductor length, multiple insulators are stacked, with the heater legs wound around insulators at different levels in the stacked configuration. In this manner, the heating element of the thermal management device is selected to provide a specified thermal output, and the heater legs are configured on one or more layers to provide the resistance necessary to achieve the specified thermal output at the operating voltage and current of the thermal management device.
- While a spiral pattern winding configuration of the heater leg has been described above, the heater leg may be provided in other configurations. Referring now to
FIG. 5 , aheating element 90 includes aheater leg 96 secured to amica insulator 92 in a hook-and-ladder configuration. As shown, theheater leg 96 is secured to the edge of theinsulator 92 bynotches 94. Theheater leg 96 passes throughnotches 94 and is retained underneath theinsulator 92 as illustrated by dashedlines 98. In one embodiment, both a spiral pattern winding and a hook-and-ladder configuration are used to secure a heater conductor to an insulator, such as by using a spiral pattern winding for at least a portion of the insulator while using a hook-and-ladder attachment adjacent at least one end of the insulator. - Referring now to
FIG. 6 , yet another embodiment of a heating element is illustrated supported by an insulator comprising two insulator panels. In one embodiment, theheating element 100 includes afirst portion 102 of a heater leg supported onfirst insulator panel 104. Theheating element 100 also includes asecond portion 106 of a heater leg supported on asecond insulator panel 108. A connectingportion 110 of the heater leg connects thefirst portion 102 and thesecond portion 106 of the heater leg and spans between thefirst insulator panel 104 and thesecond insulator panel 108. In one embodiment, the first and second insulator panels are supported on a third insulator panel, such that the first and second insulator panels lie in substantially the same plane. In another embodiment, the first insulator panel and second insulator panel are stacked vertically with a separation insulator panel in between and with the connectingportion 110 of the heater conductor extending around an edge of the separation insulator panel. In another embodiment, the heater leg spans more than two insulator panels, each connected by a connecting portion of the heater leg. In one embodiment, the spacing between successive windings is between (and including) 10 millimeters and 50 millimeters. In another embodiment, the spacing between successive windings is between (and including) 25 millimeters and 45 millimeters. In this manner, a heating element of the thermal management device is configurable into a variety of desired shapes and topologies to accommodate different operating environments and configurations. - In yet other embodiments, the heating element of the thermal management device includes two or more heater legs electrically connected in parallel to supply thermal energy. Having a plurality of heater legs connected in electrical parallel may increase the operational life of thermal management device. In some applications, after an initial start up period, a thermal management device is utilized at less than 50%, or even less than 25% of its total heat output capability. As such, a heating element with two or more heater legs may be capable of providing the necessary heat output even if one or more of the heater legs is damaged or becomes otherwise inoperative. For example, a heating element with four heater legs may be capable of producing 25% of its total heat output with only one of the four heater legs operational. In some embodiments, the expected operating life of a thermal management device is at least 10 years, and in other embodiments, the expected operating life is 20 years or greater. Over this operating lifespan, one or more heater legs may become inoperative, but the thermal management device may remain operational by maintaining sufficient heat output capability from the remaining functional heater leg or legs.
- Referring now to
FIG. 7 , an embodiment of aheating element 114 of a thermal management device is illustrated with two electrically parallel heater legs wound in an interleaved spiral pattern around aninsulator 116. As shown, theheating element 114 includes afirst heater leg 118 and asecond heater leg 120. Thefirst heater leg 118 and thesecond heater leg 120 are electrically connected in parallel, each providing one half of the device's heat output. Due to the parallel connection, if either heater leg fails, the other heater leg may remain operational, providing up to one half of the device's maximum heat output capability. Thefirst heater leg 118 andsecond heater leg 120 are each wound in a spiral pattern around theinsulator 116. As previously discussed, in other embodiments, the heater legs are wound around more than one insulator. In another embodiment, thefirst heater leg 118 is wound around a first insulator, while thesecond heater leg 120 is wound around a second insulator and each heater leg is connected to a common bus bar that provides the parallel electrical connection between the heater legs. - Referring now to
FIG. 8 , another embodiment of a heating element is illustrated having four parallel heater legs. As shown,heating element 122 includes aninsulator 124 and fourparallel heater legs insulator 124. In this embodiment, each heater leg provides approximately one fourth of the total heat output when all legs are functional. When up to three legs are inoperative, the heating element may still provide up to one fourth of the maximum heat output of the device, which, in some embodiments, is sufficient for the thermal management device to remain operational, thereby extending the useful life and reducing maintenance and repair costs. - Referring now to
FIG. 9 , yet another embodiment of aheating element 134 is shown having two electrically parallel legs. Theheating element 134 includes aninsulator 136 supporting afirst heater leg 138 and asecond heater leg 140. In one embodiment, thefirst heater leg 138 and thesecond heater leg 140 are supported on one side of theinsulator 136 without being secured to the edges of theinsulator 136. In another embodiment, thefirst heater leg 138 and thesecond heater leg 140 are woven through a series of holes (not shown) in theinsulator 136 to secure the heater legs in place. In yet another embodiment, the first and second heater legs are placed on theinsulator 136 and a second insulator (not shown) is placed on top of the heater legs and attached to theinsulator 136 to retain the heater legs in the desired location. In multiple embodiments, thefirst heater leg 138 and thesecond heater leg 140 are connected in parallel by afirst connection 142 and asecond connection 144, which may be bus bars or other electrical connections joining the heater legs in an electrically parallel configuration. A pair of positivelead wires 146 connect to thefirst connection 142, while a pair of negativelead wires 148 connect to thesecond connection 144. In this manner, the thermal management device may remain operational even if one of each pair of lead wires were to be damaged or disconnected. - In one embodiment, a thermal management device includes a single heating element having a single leg disposed on a single layer. In other embodiments, a thermal management device includes a single heater element having two or more legs on a single layer. In yet other embodiments, a plurality of heating elements including a plurality of heater legs are disposed on one two or more layers within a thermal management device. Referring now to
FIG. 10 , a portion of a thermal management device having multiple layers is illustrated. As shown, the thermal management device includes a plurality of insulators, including fiveinsulator panels metal ribbon 82 extending throughholes 84 provided in each of the insulator panels. In one embodiment, thefirst insulator panel 74 and thesecond insulator panel 78 support spiral wound heater legs of the heating element of thethermal management device 70. Thethird insulator panel 76 provides electrical insulation between the heater legs supported by thefirst insulator panel 74 and thesecond insulator panel 78, while thefourth insulator panel 72 and thefifth insulator panel 80 provide electrical insulation for the top and bottom surfaces of the thermal management device and protect the heater legs within. In one embodiment, themetal ribbon 82 forms a retention device with a maximum use temperature of at least 500 degrees Celsius that secures insulator panels of the thermal management device to each other. Alternatively or in addition to themetal ribbon 82, other retention devices, such as metal or non-conductive wire, may be used to secure a plurality of insulator panels to each other. In yet another embodiment, rivets may be used to secure the plurality of insulator panels to each other. In one embodiment, the plurality of insulator panels are flexibly connected such that the insulator panels may move relative to each other as the panels expand and contract with changes in temperature. - Referring now to
FIGS. 11 through 13 , other embodiments of thermal management devices having multiple layers are illustrated in side view. As shown inFIG. 11 , athermal management device 150 includes afirst heating element 152 and asecond heating element 154. In one embodiment, thefirst heating element 152 and thesecond heating element 154 each include a heater leg (not shown) wound in a spiral pattern around an insulator. In other embodiments, thefirst heating element 152 and thesecond heating element 154 include two or more heater legs. Thefirst heating element 152 and thesecond heating element 154 are separated by aseparation insulator 156. In one embodiment, the separation insulator is a single sheet of mica. In other embodiments, two or more sheets of mica are used to separate adjacent heating elements. Thethermal management device 150 also includes atop insulator 158 and abottom insulator 160. In one embodiment, thetop insulator panel 158 and thebottom insulator panel 160 each are one or more sheets of mica insulation and are secured with metal ribbon. - Referring now to
FIG. 12 , athermal management device 162 includes a heating element with fourheater legs 166, where each heater leg is disposed on a separate layer of the thermal management device interposed withseparation insulators 164. In one embodiment, theheater legs 166 are each connected to a common bus bar that is connected to lead wires (not shown) extending out of the thermal management device. Thethermal management device 162 also includes atop insulator 170 and abottom insulator 168 which bound the thermal management device and further protect the heater legs. As shown, each heater leg spans substantially the entire cross-section of the thermal management device, such as at least 90% of the cross-sectional area, providing a substantially uniform heat flux to the outer surfaces of the thermal management device. In some embodiments, with all heater legs operational the heat flux at thebottom insulator 168 varies by no more than 25% from the average heat flux over the full surface ofbottom insulator 168. In another embodiment, the heat flux varies by no more than 20% from the average heat flux across thebottom insulator 168 when all heater legs are operational. - Referring now to
FIG. 13 , athermal management device 174 with a plurality of heating elements each with a plurality of heater legs is illustrated. Thethermal management device 174 includes atop insulator 176, abottom insulator 178, and aseparation insulator 180. A first heating element is disposed between theseparation insulator 180 and thetop insulator 176, and a second heating element is disposed between theseparation insulator 180 and thebottom insulator 178. Each heating element includes two heater legs electrically connected in parallel. As shown, the first heating element includes twoheater legs thermal management device 174. The second heating element includes twoheater legs top insulator 176 or thebottom insulator 178 of thethermal management device 174. By combining one or more heating elements, each having one or more heater legs, a thermal management device is configurable in various embodiments to provide the desired heat flux in a size and shape appropriate to the application. - In one embodiment, the heater leg of the heating element is a resistive wire formed of a suitable conductor. Thermal energy or heat is generated when a current is passed through the resistive wire. In various embodiments, the length of the resistive wire or other resistive element is selected to provide a desired total resistance corresponding to the heat generation required to be produced by the thermal management device.
- In some embodiments, the heater leg includes a resistive wire having a round or rectangular cross-section. A rectangular cross-section may provide a larger footprint for the resistive wire to contact the insulator reducing stress on the wire and the insulator. In one embodiment, the heater leg is a nickel-chromium alloy resistive wire, such as nichrome, with a maximum use temperature of at least 1000 degrees Celsius. For example, the nichrome may be Ni60Cr16Fe24, Ni80Cr20, or other nickel-chromium alloys. In one embodiment, the nickel-chromium alloy is at least 75% nickel and, at least 15% chromium by weight, such as 80% nickel and 20% chromium by weight. In another embodiment, the heater leg is an iron-chromium-aluminum alloy resistive wire with a maximum use temperature of at least 1000 degrees Celsius. In yet another embodiment, the heater leg is a nickel-iron alloy resistive wire with a maximum use temperature of at least 500 degrees Celsius. In yet another embodiment, the heater leg is a copper-nickel alloy resistive wire with a maximum use temperature of at least 500 degrees Celsius. In yet other embodiments, the heater leg is a resistive wire formed of an alloy containing essentially no carbon. In some embodiments, the heater leg has a high oxidation resistance. The heater leg may be a solid conductor or a braided conductor.
- As previously noted, embodiments of the thermal management device include lead wires configured to provide a parallel electrical connection between a current source and the heating element. In some embodiments, the lead wires provide a parallel electrical connection between two or more electrically parallel heater legs of the heating element and the current source. The lead wires are formed of a conductive material, and may be either a solid conductor or a braided conductor. In one embodiment, the lead wires are formed of a commercial grade pure nickel, such as nickel-200. In one embodiment, nickel-200 is greater than 99.5% nickel. A lead wire formed of nickel-200 provides a high electrical conductivity and high corrosion resistance. Nickel-200 also has a maximum use temperature of at least 1400 degrees Celsius, allowing for prolonged use in high temperature applications. In another embodiment, the lead wires are formed of nickel-201, a commercially pure wrought nickel with similar properties to nickel-200. In some embodiments, nickel-201 may have a lower carbon content than nickel-200 and may resist carbon embrittlement from prolonged use at elevated temperatures. Nickel-201 also provides high electrical conductivity and high corrosion resistance. In yet other embodiments, the lead wires are formed of copper, nickel-plated copper, aluminum, stainless steel, a nickel alloy, or other conductive material.
- In various embodiments, the thermal management device includes a pair of positive lead wires connecting to a first pole of a heating element and a pair of negative lead wires connecting to a second pole of a heating element, such as illustrated in
FIGS. 1 and 2 . In some embodiments, the thermal management device includes two or more heating elements and Multiple pairs of lead wires, with each pair of lead wires connecting to one of the poles of one of the heating elements. In operation, each lead wire of a given pair supports approximately one half of the current supplied to the heating element. In other embodiments, more than two lead wires are provided for each pole of each heating element and each lead wires carries less than one half of the current supplied to the heating element. In some embodiments, during the startup phase of the thermal management device, a maximum heat output is generated and a maximum current flows through the lead wires. During subsequent operations, the thermal management device may be operated at no more than 50%, or no more than 25% of its total capacity, with a corresponding reduction in the current required. In one embodiment, each lead wire is designed to supply at least 50% of the total maximum current, and during subsequent operations, the thermal management device may remain operational even if one of the lead wires is damaged or otherwise inoperative. In this manner, the lead wires provide improved fault tolerance for the thermal management device and may extend the operational life of the thermal management device, thereby reducing costs for maintenance and repair. - The lead wires of the thermal management device extend out of the body or main part of the thermal management device to connect to a current source to power the heating elements. In one embodiment, the lead wires are provided with insulation to maintain electrical isolation between the lead wires and a housing or cover of the thermal management device. In other embodiments, the lead wire insulation also provides mechanical protection to protect the lead wires against wear or damage as the lead wires are moved during installation or operation of the thermal management device. For example, various components of the thermal management device or surrounding application may expand and contract as a result of temperature changes over the lifespan of the thermal management device, causing movement of the lead wires relative to other components in the system. Movement of lead wires has in the past resulted in abrasion of the lead wire insulation and even damage to the conductors of the lead wires. Additionally, bending of lead wires around corners and other structures has further limited the reliability of thermal management devices. To mitigate damage to the lead wire conductor, the lead wire insulator provides mechanical protection to the conductor during movement of the lead wire. In one embodiment of the present system, the lead wires are insulated with an electrically insulating material having a maximum use temperature of at least 400 degrees Celsius. In another embodiment, the lead wires are insulated with an abrasion resistant material. In one embodiment, the lead wire insulation is a polytetrafluoroethylene (PTFE) (e.g., Teflon® brand) coated fiberglass insulation. PTFE is a synthetic fluoropolymer of tetrafluoroethylene that finds numerous applications. PTFE is most well known by the DuPont brand name Teflon. In another embodiment, the lead wire insulation is a mica-PTFE-fiberglass insulation (“MTG”). In one embodiment, the MTG insulation includes a combination of fiberglass, PTFE tape, and phlogopite mica tape. In yet another embodiment, the lead wires are protected by a metal braided mesh covering. In yet other embodiments, the lead wire insulation is a polymide insulation, phenolics insulation, cement insulation, ceramic insulation, or combinations thereof. In various embodiments, the temperature within a battery enclosure is approximately 300 degrees Celsius and the current flow through the lead wires may increase the temperature of the lead wire insulation up to 400 degrees Celsius. In these embodiments, the lead wire insulation has a maximum use temperature of at least 400 degrees Celsius. In other embodiments, the current flow through the lead wire is limited such that the maximum use temperature of the lead wire insulation is not exceeded during operation of the thermal management device.
- The thermal management device may also have one or more strain reliefs provided for the parallel lead wires. In prior systems, mechanical failure of lead wire connections have rendered battery heaters inoperative, and as a result, required replacement or repair of rechargeable battery systems. Providing one or more strain reliefs for the lead wires may thus improve the reliability of the thermal management device, extending the operational life and reducing maintenance and repair costs of a system employing the thermal management device.
- Referring now to
FIG. 14 , a strain relief for use with the thermal management device is illustrated. Astrain relief block 200 is attached to theinsulator 202, such as a mica sheet. In one embodiment, thestrain relief block 200 is attached to theinsulator 202 byrivets 204. In other embodiments, thestrain relief block 200 is attached to theinsulator 202 by other mechanical or adhesive connections compatible with the operating temperature of the thermal management device. In one embodiment, thestrain relief block 200 is positioned so as to reduce the length of the lead wires extending out of a housing for the thermal management device. As shown, alead wire 206 havinglead wire insulation 208 extends towards thestrain relief block 200. A portion of the conductor of thelead wire 206 is exposed and mechanically secured to thestrain relief block 200 atfirst connection 210. Similarly, a portion of the conductor of aheater leg 212 is mechanically secured to thestrain relief block 200 at asecond connection 214. Additionally, thelead wire 206 and theheater leg 212 are electrically connected at thestrain relief block 200. In one embodiment, thestrain relief block 200 provides an electrical connection between thefirst connection 210 and thesecond connection 214 to transfer current from thelead wire 206 to theheater leg 212. In some embodiments, thestrain relief block 200 provides a connection for asingle heater leg 212 and asingle lead wire 206, such as shown inFIG. 14 . In other embodiments, a strain relief block may include a plurality of first connections each configured to connect one or more lead wires, and a plurality of second connections each configured to connect one or more heater legs. In yet another embodiment, two or more strain relief blocks may be provided to support the lead wires and heater legs of the thermal management device. Connecting thelead wire 206 and theheater leg 212 to thestrain relief block 200 reduces stress on the electrical connection between the lead wire and the heater leg as the lead wires are routed through a housing, or manipulated during assembly or installation of the thermal management device. - Referring now to
FIG. 15 , one embodiment of a strain relief connection is illustrated, where the lead wires are connected to the strain relief by a weld connection and by a mechanical connection. As shown, alead wire 220 is connected to astrain relief pad 222 by aweld connection 224. In various embodiments, the weld connection includes a brazing or a solder connection when the operating temperature of the thermal management device is below the melting temperature of a connection formed using those technologies. In one embodiment, temperatures near the weld connection may reach 800 degrees Celsius and a welded joint with a melt temperature of at least 800 degrees Celsius is utilized. Alternatively or in addition, thelead wire 220 is also secured to thestrain relief pad 222 bymechanical connections 226 on either side of theweld connection 224. In one embodiment, themechanical connections 226 maintain the electrical connection between thelead wire 220 and a conductive portion of thestrain relief pad 222. In another embodiment, theweld connection 224 may connect thelead wire 220 to a conductor of a heater leg and may or may not form a welded connection to thestrain relief pad 222. In one embodiment, the mechanical connection includes a twist tie. In other embodiments, the mechanical connection includes folding or wrapping the lead wire around a portion of thestrain relief pad 222. The mechanical connection may be selected based on the operating temperature of the thermal management device. For some applications polymer tapes are utilized. In yet another embodiment, themechanical connection 226 includes rivets used to secure thelead wire 220 to thestrain relief pad 222. As noted above, thestrain relief pad 222 is secured to theinsulator 230 byrivets rivets strain relief pad 222 to theinsulator 230 are positioned between theweld connection 224 and themechanical connections 226 to improve the distribution of forces applied to the lead wire. In one embodiment, the thermal management device is manufactured by securing a lead wire to the strain relief by welding prior to securing the mechanical connections on either side of the welded connection to minimize stress on the lead wire during installation. - Referring now to
FIG. 16 , yet another embodiment of a strain relief for use in a thermal management device is illustrated. In one embodiment, alead wire 240 is welded to a conductor of aheater leg 242 by aweld 244. Theweld 244 establishes both an electrical and mechanical connection between thelead wire 240 and theheater leg 242 and avoids the introduction of oxides between the conductors. The strain relief also includes acrimp tube 248. In one embodiment, thelead wire 240 andheater leg 242 are positioned within thecrimp tube 248, and all three components are welded together as illustrated by theweld 244. In one embodiment, crimpconnections 246 are provided on either side of theweld 244 to provide mechanical support to the lead wire and heater leg. Thecrimp connections 246 absorb and dissipate stresses resulting from movement of thelead wire 240, further protecting the weld connection. In yet another embodiment, a combination of mechanical connections, such as twisted, tied, folded, crimped, or riveted, are used to secure the lead wire and heater leg to the strain relief. - Referring now to
FIG. 17 , a top view of a thermal management device with another embodiment of a strain relief for the lead wires is illustrated. In one embodiment, thethermal management device 250 includes afirst insulator 258, and asecond insulator 256. One or more heating elements (not shown) are disposed between the first and second insulators as previously discussed. In one embodiment, thefirst insulator 258 is a center panel within a generally symmetric arrangement of insulator panels and heating elements are provided both above and below the center panel. A pair of positivelead wires 252 may extend from a firststrain relief block 262 secured to thefirst insulator 258, where the positive lead wires are electrically connected to at least one heater leg atconnection 264. A pair of negativelead wires 254 may extend from a secondstrain relief block 266 secured to the first insulator, where the negative lead wires are electrically connected to at least one heater leg atconnection 268. In other embodiments, the strain relief blocks are not utilized and the lead wires may be connected to the heater legs by other methods. Thefirst insulator 258 of thethermal management device 250 also includes a plurality ofapertures 260 configured for routing the pair of positivelead wires 252 and the pair of negativelead wires 254. As shown, the lead wires may be laced through theapertures 260 extending on alternating sides of the insulator between adjacent apertures. In one embodiment, to maintain separation, the positivelead wires 252 are laced through apertures separate from the apertures used for negativelead wires 254. Although theapertures 260 are illustrated in a generally circular configuration, apertures of other shapes may also be used. In this manner, thefirst insulator 258 havingapertures 260 provides a strain relief for the lead wires. If tension is applied to the lead wires, the resulting stresses may be at least partially transferred to thefirst insulator 258 as the lead wires pull against the edges of theapertures 260. In this manner, the electrical and mechanical connections of the lead wires are further protected against breakage or other damage. - Referring now to
FIG. 18 , aninsulator 270 is illustrated with another embodiment of a strain relief for the lead wires of the thermal management device. Theinsulator 270 supports one or more heater legs. A portion of aheater leg 282 is illustrated connected to alead wire 275 byweld 280. In one embodiment, theinsulator 270 is provided with afirst channel 272 extending through the insulator. Thefirst channel 272 is configured to receive a first pair oflead wires FIG. 18 , theinsulator 270 also includes asecond channel 274 extending through the insulator panel. Thesecond channel 274 is configured to receive a second pair oflead wires 278. Each one of the first pair oflead wires first channel 272. As illustrated, thefirst channel 272 is substantially U-shaped and each one of the pair of firstlead wires first channel 272. In other embodiments, thefirst channel 272 may include two sections that are unconnected. The width of thefirst channel 272 is sized to accommodate the diameter of thelead wires first channel 272 is substantially the same dimension as the lead wire diameter, such as between 95% and 105% of the lead wire diameter. In another embodiment, the width of thefirst channel 272 is between 98% and 102% of the lead wire diameter. In another embodiment, the width of thefirst channel 272 is substantially equal to the diameter of thelead wires first channel 272 provides a strain relief as forces on the lead wire are at least partially transmitted to theinsulator 270. In one embodiment, thelead wires heater leg 282 by welds, such as theweld 280 illustrated for thelead wire 275. In a similar manner, the second pair oflead wires 278 are retained and strain-relieved bysecond channel 274, and connected to a heater leg byweld 284. - In one embodiment, the
weld 280 is disposed within thefirst channel 272 such that the weld does not increase the overall thickness of the thermal management device. In some embodiments, the overall thickness of the thermal management device is equal to the thickness of an upper and lower insulation panel plus the diameter of the lead wire disposed between the upper and lower insulation panels in thefirst channel 272. - In one embodiment, illustrated in
FIG. 19 , the first pair oflead wires 276 extend from the first channel through afirst hole 286 provided in abottom insulator 290. Similarly, the second pair oflead wires 278 extend from the second channel through asecond hole 288 provided in thebottom insulator 290. In other embodiments, thefirst hole 286 and thesecond hole 288 may be provided in a top insulator when it is desired to route the lead wires out the top side of the thermal management device. Alternatively, thefirst hole 286 and thesecond hole 288 may be provided on opposite sides of the thermal management device when it is desired to route the positive and negative lead wires on opposite sides of the thermal management device. In yet other embodiments, one hole may be provided for each of the lead wires to accommodate other configurations and applications, or a single hole may be provided for all lead wires. As illustrated, the lead wires are routed at approximately a 90° angle from the channel of an interior insulator through the hole in an exterior insulator, for providing additional strain relief. The interior and exterior insulators may be joined bymetal ribbon 292 such that the lead wires are secured in the channel of the interior insulator. In yet another embodiment, the strain relief provided by the channel and hole may be used in connection with one or more of the strain relief systems previously discussed. - Referring now to
FIG. 20 , a thermal management device in which each of the electrically parallel heater legs is configured to provide substantially uniform heat flux over at least one surface of the thermal management device is shown. In the embodiment illustrated, thethermal management device 300 includes aheating element 310 disposed within ahousing 302. Thehousing 302 has a top surface and a bottom surface (not shown). In one embodiment, thethermal management device 300 is positioned within a battery enclosure above a plurality of energy storage cells such that heat flux across the bottom surface of thehousing 302 heats the energy storage cells to a desired operating temperature and maintains the energy storage cells at the desired operating temperature as needed throughout the lifespan of the battery system. As shown, theheating element 310 includes afirst heater leg 312 and asecond heater leg 314. Thefirst heater leg 312 and thesecond heater leg 314 are electrically connected in parallel and each is connected to a firststrain relief block 322 and a secondstrain relief block 324. The firststrain relief block 322 and the secondstrain relief block 324 are each connected to an insulator 316 (e.g., a mica insulator panel) about which the first and second heater legs are wound in a spiral pattern. A pair of positivelead wires 318 are connected to the firststrain relief block 322, and extend out of thehousing 302 through anaperture 304. A pair of negativelead wires 320 are connected to the secondstrain relief block 324 and extend out of thehousing 302 through theaperture 306. In this fashion, thethermal management device 300 is configured to generate heat for a battery system by passing current through positive lead wires; first and second heater legs, and negative lead wires. Additionally, thethermal management device 300 may remain operational in the event of a failure of one lead wire of each pair, or one of the first and second heater legs. - As shown in
FIG. 20 , thefirst heater leg 312 and thesecond heater leg 314 are each configured to provide substantially uniform heat flux over the top surface and/or bottom surface of thethermal management device 300. In one embodiment, a substantially uniform heat flux over a surface is defined as a local heat flux that varies by no more than 25% from the average heat flux over the footprint defined by the heater legs of the thermal management device. In another embodiment, a substantially uniform heat flux over a surface is defined as a local heat flux that varies by no more than 20% from the average heat flux over the footprint defined by the heater legs of the thermal management device. In yet another embodiment, a substantially uniform heat flux is defined as a local heat flux in any one square inch region that varies by no more than 25% from the average heat flux over the footprint defined by one leg of a heating element of the thermal management device. In yet another embodiment, each heating element is configured to provide uniform heat flux over at least 20% of one surface of the device. In yet another embodiment, each heater leg is configured to provide uniform heat flux over at last 20% of one surface of the thermal management device. A thermal management device configured to provide a substantially uniform heat flux may result in a more even heating of the energy storage cells or other structures being heated. Additionally, a thermal management device having a plurality of heater legs with each heater leg configured to provide substantially uniform heat flux over at least 90% of the surface, if a heater leg is damaged or become inoperative, the remaining operational heater leg(s) may still provide a substantially uniform heat flux to the energy storage cells or other structuring being heated. - Referring now to
FIG. 21 , another embodiment of athermal management device 350 is illustrated that may provide non-uniform heat flux over at least one surface of the thermal management device. As shown, thethermal management device 350 has a heating element including a plurality of heater legs each supported on an insulator within ahousing 352. In one embodiment, a first heater leg 354 provides a first heating region corresponding to a portion of the area to be heated, and asecond heater leg 356 provides a second heating region corresponding to a different portion of the area to be heated. In one embodiment, the first heating region corresponds to an interior portion of an energy storage device, and the second heating region corresponds to a perimeter region of an energy storage device with a greater thermal loss than the interior region of the energy storage device. - As described below, it may be desired to achieve a substantially uniform temperature in a structure employing a thermal management device, such as an energy storage device. As the structure being heated may have greater heat loss in some regions than in others, the thermal management device may be configured to provide greater heat flux in the regions where the structure has the greater heat loss. For example, an energy storage device may have greater heat loss around the perimeter of the device, resulting in energy storage cells near the perimeter having a lower temperature than energy storage cells in an interior portion of the device. In one embodiment, the
thermal management device 350 is configured to at least partially compensate for the uneven heat distribution by providing increased heat flux to those regions where the energy storage device experiences greater thermal losses. - In one embodiment, the first heater leg 354 provides a first heating region, where the first heating region corresponds to (e.g., is primarily configured to impart thermal energy to) an interior portion of an energy storage device. The
second heater leg 356 provides a second heating region, where the second heating region corresponds to at least a portion of a perimeter of an energy storage device having greater heat loss than the interior portion. The first and second heater legs are configured such that the second heating region has a heat flux at least 25% greater than the heat flux of the first region. In other embodiments, the heat flux of the second heating region is between (and including) 10% and 25% greater than the heat flux of the first heating region. The difference in the desired heat flux between the first and second heating regions may be selected based on thermal characteristics of the specific structure or application to be heated by the thermal management device. - As illustrated in
FIG. 21 , thethermal management device 350 may also include athird heater leg 358, afourth heater leg 360, and afifth heater leg 362 extending substantially around the perimeter of the thermal management device. In one embodiment, the plurality of heater legs define one or more additional heating regions providing a heat flux selected to achieve a substantially uniform temperature among the energy storage cells of an energy storage device. - Referring now to
FIGS. 22 through 24 , the operation of a thermal management device having a non-uniform heat flux is illustrated. In one embodiment, an energy storage device may have a temperature gradient across the energy storage cells of the device. Such a temperature gradient may result in an energy storage cellthermal profile 370 along a cross section of the energy storage device, such as illustrated inFIG. 22 , where the relative temperature of the energy storage cells is indicated by the length of the bars in thethermal profile 370. As indicated by thethermal profile 370, the cells near the perimeter of the energy storage device may have a lower temperature because ofheat loss 372 from the sides of an enclosure. In contrast, the cells in theinterior portions 374 of the energy storage device may have a relatively higher temperature as indicated. In these and other applications, athermal management device 380 may be provided having a non-uniformheat flux profile 382, such as illustrated inFIG. 23 . The amount of heat flux from the thermal management device is illustrated by the length of the arrows of theheat flux profile 382. As shown, the non-uniformheat flux profile 382 includes regions of relatively greater heat flux corresponding to the regions near the perimeter of the energy storage device where thermal loss may be greatest. The non-uniformheat flux profile 382 may also have regions of lower heat flux corresponding to interior portions of the energy storage device where thermal loss is reduced. Theheat flux profile 382 may have a gradual transition as illustrated or may include one or more discrete levels. In one embodiment, the heat flux between a first region, such as near the perimeter, may be at least 15%, at least 25%, or at least 50% greater than the heat flux in a second region, such as an interior portion. As shown, the thermal management device has theheat flux profile 382 illustrated inFIG. 23 that corresponds thethermal profile 370 of the energy storage device illustrated inFIG. 22 . In this manner, an energy storage device may achieve a uniform cell temperature illustrated bythermal profile 390, even withheat loss 392 from the perimeter of the device. The temperature of energy storage cells in theinterior portion 394 is maintained substantially the same as the temperate of the energy storage cells adjacent the perimeter where theheat loss 392 is greater. In various embodiments, the configuration of heater legs, or the position of the heater legs or heating elements may be adjusted to achieve the desired heat flux profile. In other embodiments, the thermal management device may include two or more independently controllable heating elements and a control system may be provided to operate the heating elements to achieve the desired heat flux profile. -
FIGS. 25 and 26 show an embodiment of anenergy storage device 400 having athermal management device 402. Theenergy storage device 400 includes thethermal management device 402 and a plurality ofenergy storage cells 404 disposed within abattery enclosure 406. In one embodiment, thethermal management device 402 is positioned above thecells 404. In other embodiments however, the thermal management device is positioned below or between the cells. In yet another embodiment, two or more thermal management devices are provided within the battery enclosure to achieve the desired heating of the cells. In one embodiment, the cells are sodium-metal-halide cells having an operating temperature of approximately 300 degrees Celsius. During a startup phase, thethermal management device 402 provides a maximum heat output to heat the cells to the desired operating temperature. The heat output is then reduced or discontinued as necessary to maintain the cells within a desired operating range, such as between (and including) 280 degrees Celsius and 320 degrees Celsius. - In one embodiment, the
battery enclosure 406 includes alead wire aperture 408 for the lead wires of the thermal management device to exit the battery enclosure. The battery enclosure also includes apower connector 410 configured to connect the power and control signals from the energy storage cells and battery management system. In one embodiment, the battery enclosure also includes a pair of coolingports 412 configured to transfer cooling fluid into and out of the battery enclosure to cool theenergy storage cells 404 as needed during operation. In one embodiment, the lead wire aperture, power connector, and ports are located on afirst side 422 of the battery enclosure that is opposite asecond side 424 of thebattery enclosure 406. - In some embodiments, it is desired to maintain all of the energy storage cells at a substantially uniform temperature even when one or more heater legs are inoperative, however, the thermal losses from the energy storage device may be asymmetric resulting in a temperature gradient across the energy storage cells. Referring now to
FIG. 26 , the energy storage device is illustrated with the heater legs ofthermal management device 402 exposed. As shown, thethermal management device 402 has fourheater legs 420, each wound in a spiral pattern around a mica panel or other insulator. The fourheater legs 420 are electrically connected in parallel. Theheater legs 420 are oriented to extend generally between thefirst side 422 and thesecond side 424 of the energy storage device. In one embodiment, thefirst side 422 of theenergy storage device 400 has a greater thermal loss than thesecond side 424. For example, the presence oflead wire aperture 408,power connector 410, and coolingports 412 extending throughfirst side 422 may reduce the thermal resistance offirst side 422 of thebattery enclosure 406, thereby increasing the thermal loss through the first side. In other embodiments, the orientation of theenergy storage cells 404 withinbattery enclosure 406 may result in a disproportionate thermal loss on one side of the energy storage device. - In another embodiment, the
energy storage device 400 has afirst axis 426 extending between opposing sides, such asfirst side 422 andsecond side 424. Theenergy storage device 400 also has asecond axis 428 perpendicular to thefirst axis 426. In one embodiment, the temperature gradient across theenergy storage cells 404 is greater along thefirst axis 426 than the temperature gradient across theenergy storage cells 404 along thesecond axis 428. In this embodiment, the heater legs of the heating element may be aligned with thefirst axis 426. When all four heater legs are operational, the heat flux from the thermal management device to the energy storage cells is substantially uniform and the variation in temperature among the energy storage cells is reduced. However, in some embodiments, having the heater legs aligned with thefirst axis 426, between thefirst side 422 and thesecond side 424, may maintain a more uniform temperature distribution among the energy storage cells even when one or more of the heater legs is inoperative. - Referring now to
FIG. 27 , a simulated thermal profile in degrees Kelvin is illustrated for the cells of an energy storage device having a thermal management device. As illustrated, the energy storage cell temperature gradient is predicted to be greater along thefirst axis 426 than along thesecond axis 428. With uniform heat flux from the thermal management device, the maximum simulated temperature of the energy storage cells is 582 degrees Kelvin, while the minimum simulated cell temperature is 558 degrees Kelvin, resulting in a total variation in cell temperature of 24 degrees Kelvin, which may be within the acceptable range for the selected cell chemistry. - Referring to
FIG. 28 , also disclosed is athermal management device 500 comprising a pair of heating elements in a stacked arrangement. Thethermal management device 500 includes afirst heating element 504 connected to apositive lead wire 506 and anegative lead wire 508. The thermal management device also includes asecond heating element 516 connected to apositive lead wire 512 and anegative lead wire 514. In one embodiment, thefirst heating element 504 is operationally connected and used during operation of the thermal management device, while thesecond heating element 516 is not connected and is provided as a spare or backup heating element in the event of a failure of the first heating element. In this manner, thesecond heating element 516 provides a built in replacement or substitute for thefirst heating element 504. In this embodiment, thefirst heating element 504 and thesecond heating element 516 are each capable of providing the necessary heat flux to an application such that only one heating element is required for operation. In some applications, replacement of the thermal management device may not be feasible and having a spare heating element may provide a cost effective means of returning an application to a functional state after failure of a heating element. - As presently disclosed, a thermal management device provides improved reliability, and more uniform cell temperatures as compared to devices of the prior art. In the various embodiments, the thermal management device may achieve an operational life span matching or exceeding the twenty year life expectancy of certain rechargeable battery systems thereby reducing maintenance and repair costs.
- In the appended claims, the terms “including” and “having” are used as the plain-language equivalents of the term “comprising”; the term “in which” is equivalent to “wherein.” Moreover, in the following claims, the terms “first,” “second,” “third,” “upper,” “lower,” “bottom,” “top,” etc. are used merely as labels, and are not intended to impose numerical or positional requirements on their objects. Further, the limitations of the following claims are not written in means-plus-function format and are not intended to be interpreted based on 35 U.S.C. §112, sixth paragraph, unless and until such claim limitations expressly use the phrase “means for” followed by a statement of function void of further structure. As used herein, an element or step recited in the singular and proceeded with the word “a” or “an” should be understood as not excluding plural of said elements or steps, unless such exclusion is explicitly stated. Furthermore, references to “one embodiment” of the present invention are not intended to be interpreted as excluding the existence of additional embodiments that also incorporate the recited features. Moreover, unless explicitly stated to the contrary, embodiments “comprising,” “including,” or “having” an element or a plurality of elements having a particular property may include additional such elements not having that property. Moreover, certain embodiments may be shown as having like or similar elements, however, this is merely for illustration purposes, and such embodiments need not necessarily have the same elements unless specified in the claims.
- As used herein, the terms “may” and “may be” indicate a possibility of an occurrence within a set of circumstances; a possession of a specified property, characteristic or function; and/or qualify another verb by expressing one or more of an ability, capability, or possibility associated with the qualified verb. Accordingly, usage of “may” and “may be” indicates that a modified term is apparently appropriate, capable, or suitable for an indicated capacity, function, or usage, while taking into account that in some circumstances the modified term may sometimes not be appropriate, capable, or suitable. For example, in some circumstances an event or capacity can be expected, while in other circumstances the event or capacity cannot occur—this distinction is captured by the terms “may” and “may be.”
- This written description uses examples to disclose the invention, including the best mode, and also to enable one of ordinary skill in the art to practice the invention, including making and using any devices or systems and performing any incorporated methods. The patentable scope of the invention is defined by the claims, and may include other examples that occur to one of ordinary skill in the art. Such other examples are intended to be within the scope of the claims if they have structural elements that do not differ from the literal language of the claims, or if they include equivalent structural elements with insubstantial differences from the literal language of the claims.
Claims (20)
1. A thermal management device comprising:
a plurality of insulator panels with a maximum use temperature of at least 500 degrees Celsius; and
a heating element comprising at least two heater legs electrically connected in parallel, each heater leg contacting at least one of the insulator panels and configured to supply to thermal energy,
the heating element having lead wires configured to provide a parallel electrical connection between the heater legs and a current source.
2. The thermal management device as claimed in claim 1 , wherein each of the at least two heater legs is wound in a spiral pattern around one of the insulator panels.
3. The thermal management device as claimed in claim 1 , wherein an insulator panel having a heater leg attached thereto is disposed between insulator panels not having a heater leg attached thereto.
4. The thermal management device as claimed in claim 1 , wherein two or more of the heater legs are wound in an interleaved spiral pattern around one of the insulator panels.
5. The thermal management device as claimed in claim 1 , wherein each of the at least two heater leg is configured to provide heat flux over at least about 90% of one surface of the device.
6. The thermal management device as claimed in claim 1 , wherein the lead wires include a first pair of parallel lead wires connected to a first pole of the heating element, and a second pair of parallel lead wires connected to a second pole of the heating element.
7. A thermal management device comprising:
an insulator with a maximum use temperature of at least 500 degrees Celsius; and
a heating element comprising at least two heater legs electrically connected in parallel, the heater legs contacting the insulator and configured to supply thermal energy to a plurality of energy storage cells,
wherein each of the parallel heater legs is configured to provide substantially uniform heat flux over at least one surface of the device.
8. The thermal management device as claimed in claim 7 , wherein the insulator is mica.
9. The thermal management device as claimed in claim 7 , wherein the heating element comprises a nickel-chromium alloy resistive wire.
10. The thermal management device as claimed in claim 7 , wherein the at least two heater legs are wound in an interleaved spiral pattern around the insulator.
11. An energy storage device comprising:
a plurality of energy storage cells having an operating temperature of at least 250 degrees Celsius; and
a thermal management device comprising:
an insulator with a maximum use temperature of at least 500 degrees Celsius; and
a heating element contacting the insulator and having a plurality of heater legs electrically connected in parallel, the heating element configured to supply thermal energy to the plurality of cells,
the heating element having lead wires configured to provide a parallel electrical connection between the heater legs and a current source.
12. The energy storage device as claimed in claim 11 , wherein each of the heater legs is configured to provide a substantially uniform heat flux to the plurality of energy storage cells.
13. The energy storage device as claimed in claim 11 , the thermal management device further comprising a strain relief attached to the insulator, wherein the lead wires are connected to the strain relief.
14. The energy storage device as claimed in claim 11 , wherein the heating element is one of a plurality of heating elements, the thermal management device comprising the plurality of heating elements.
15. The energy storage device as claimed in claim 11 , wherein the thermal management device is positioned within the energy storage device such that the heater legs are oriented to extend between a first side of the energy storage device and a second side of the energy storage device opposite the first side.
16. The energy storage device as claimed in claim 15 , wherein the first side of the energy storage device has greater thermal loss than the second side.
17. The energy storage device as claimed in claim 11 , further comprising:
a first axis extending between opposing sides of the energy storage device, and a second axis perpendicular to the first axis,
wherein a temperature gradient along the first axis is greater than a temperature gradient along the second axis.
18. The energy storage device as claimed in claim 17 , wherein the heater legs of the heating element are aligned with the first axis.
19. The energy storage device as claimed in claim 11 , wherein the heating element is configured to provide a first heating region and a second heating region, wherein the first heating region has a heat flux at least 25% greater than a heat flux of the second heating region.
20. The energy storage device as claimed in claim 11 , wherein the thermal management device has a heat flux profile corresponding to a thermal loss profile of the plurality of energy storage cells.
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US13/235,009 US20130071716A1 (en) | 2011-09-16 | 2011-09-16 | Thermal management device |
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US13/235,009 US20130071716A1 (en) | 2011-09-16 | 2011-09-16 | Thermal management device |
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